Please wait… 
Please wait while we process your order,
do not press the back button… 
Design 911 Design 911 supply Porsche parts, Porsche spares and Porsche accessories, to both retail and to the trade. Our Porsche product and accessory range includes brakes, exhausts, tyres, wheels and Porsche panels and interiors. https://design91.uk/images/schemaLogo.png https://design91.uk/images/schemaLogo.png +443456003478 https://design91.uk Facebook Instagram

Catalyst / Bypass

Filter by brand
DISPLAYING 1 to 8 (of 8 products)
HEATKIT986
Product Information
Product Information
Exhaust Cat Heat protection plate kit.

porsche

Fits:
Porsche Boxster 986 cat.

Click 'Zoom in' for large parts diagram.
Diagram Ref No 17,18, 25, 26 and 27.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

HEATKIT986
99611342200
99611342100
99611342100
99611342200
99950743009
90015100703
99950741308

The product you are viewing cross references to these numbers
986PO94260S
Product Information
Product Information
Exhaust 100 cell Catalytic Converter Pipes Sports

Fits:
Porsche 986 Boxster 2.5L 1997-99

Please note: These 100 cell sport cats will make your car sound louder than with stock cats. If you have, or intend to install sport silencers, you may find the car is a bit loo loud. We recommend to use one sport exhaust component if you are concerned about decibel levels.

Emissions legal horsepower - throaty sports car sound, but not too loud for every day driving, manufactured from extra heavy duty stainless steel, which eliminates the splitting, cracking and annoying resonance.

NOTE: In the United Kingdom, sports catalytic converters and bypass pipes do not have type approval and are not legally permitted for use on vehicles manufactured after 1st March 2001. They are not MOT compliant and cannot be used on public roads. These components are intended solely for race and track use.

For vehicles manufactured before 1st March 2001, a non-type approved sports catalytic converter may be fitted, provided it offers comparable performance to the original and the vehicle continues to meet the applicable emissions standards for its age. The vehicle must still pass an MOT test.

 If you are located outside the UK, please check your local laws and regulations to ensure compliance.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

986PO94260S
996113921AX
996113922AX
99611399201
99611392101
1620300810

The product you are viewing cross references to these numbers
Special Order item
99611342
Product Information
Product Information
Exhaust cat heat shield. 

porsche

Another popular item which normally rusts and starts to rattle. Heat protection plate for Porsche Boxster 986 cat.

Price is for each heat shield

Click 'Zoom in' for large parts diagram.
Diagram Ref No 19 and 20


Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99611342
99611342200
99611342100

The product you are viewing cross references to these numbers
Special Offer
3606109862
Product Information
Product Information
Exhaust catalytic converter bypass pipe for Porsche Boxster 986

designtek

Manufactured from highest quality T304 grade stainless steel
Mandrel bent and fully TIG welded for strength and durability
CNC machined flanges for strong, solid support and an accurate fit
Designed to improve power and torque across the entire RPM range
Noticeably improves throttle response
Please note fitting instructions are NOT included
Sold for off-road / track use only
We recommend all exhaust components are fitted by a qualified mechanic to ensure the correct fitment

Fits:
Porsche Boxster 986 2.5L / 2.7L / 3.2L

Please note: These sport cats will make your car sound louder than with stock cats. If you have ,or intend to install sport silencers, you may find the car is a bit loo loud. We recommend to use one sport exhaust component if you are concerned about decibel levels.

NOTE:
In the United Kingdom, sports catalytic converters and bypass pipes do not have type approval and are not legally permitted for use on vehicles manufactured after 1st March 2001. They are not MOT compliant and cannot be used on public roads. These components are intended solely for race and track use.

For vehicles manufactured before 1st March 2001, a non-type approved sports catalytic converter may be fitted, provided it offers comparable performance to the original and the vehicle continues to meet the applicable emissions standards for its age. The vehicle must still pass an MOT test.

 If you are located outside the UK, please check your local laws and regulations to ensure compliance.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

3606109862
996113921AX
996113922AX
99611392101
99611392201
99611302111
99611302112

The product you are viewing cross references to these numbers
Special Order item
99950800401
Product Information
Product Information
Heatshield Locking Bolt 6x12. EACH.

porsche

Fits:
Porsche Boxster 986


Click 'Zoom in' for large parts diagram.
Diagram ref no 27

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99950800401
99950743009
99950800401

The product you are viewing cross references to these numbers
Special Order item
90015100703
Product Information
Product Information
Heatshield Locking Bolt washer 7,4mm . EACH.

porsche

Fits:
Porsche Boxster 986

Click 'Zoom in' for large parts diagram.
Diagram ref no 26

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

90015100703
90015100703
90015100702

The product you are viewing cross references to these numbers
Special Offer
99611392
Product Information
Product Information
Standard Replacement Exhaust Catalytic Converter for Porsche Boxster 986 2.5L

designtek

Porsche Boxster 2.5L Replacement Cats made in grade 409 stainless steel. Recommend to change in a pair

Fits:
Porsche Boxster 986 2.5L

Note: You will need M8x1x10 Plug (90021901500) & M8x11.5 Seal ring (90012305020) from each original Cat or suitable replacement



A catalytic converter is an emissions control device to stop harmful exhaust gasses from entering the atmosphere. In 1993, they became legality in the UK as part of the Euro Emissions standards. The aim of them is to improve air quality. As emissions standards have become more stringent the number of cats on a vehicle has increased. Many vehicles now have two or more to enable them to meet the Euro Emissions standards.

Our cat is made up of the following components:
  • Ceramic monolith of a honeycomb design to allow free air flow and maximum surface area, coated with precious metals to enable the conversion of gasses that pass through it
  • Interam matting to hold the monolith in place. The matting expands when exposed to heat to supply the pressure needed to keep the monolith secure
  • A grade 409 stainless steel can (or housing) to provide protection and enable the cat to be built into the exhaust system. 409 grade can contain upto 90% iron and will be prone to rust. It still has higher rust-resistant properties than mild steel.


Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99611392
99611392101
99611392201
996113921AX
996113922AX

The product you are viewing cross references to these numbers
Special Order item
99950741308
Product Information
Product Information
Retaining clip Speed nut. EACH.

porsche

Fits:
Porsche Boxster 986

Diagram ref no 25

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99950741308
99611342200
99611342100
99950741308
99950741309

The product you are viewing cross references to these numbers
DISPLAYING 1 to 8 (of 8 products)
Also found on these pages
About Catalyst / Bypass

Exhaust Catalytic Converters & Bypass Pipes – Performance, Efficiency & Flow Control

The catalytic converter plays a crucial role in your Porsche’s exhaust system, reducing harmful emissions while maintaining optimal exhaust flow. Positioned between the exhaust manifold and silencer, it converts toxic gases such as carbon monoxide, hydrocarbons, and nitrogen oxides into less harmful emissions before they exit the tailpipe.

At Design911, we offer a complete range of catalytic converters and bypass pipes for Porsche vehicles. Our manufacturer-quality converters ensure reliable emission control and long-term performance, while our bypass options are designed for track or performance use, optimising exhaust flow for maximum power and throttle response.

Whether you’re maintaining your Porsche to meet emissions standards or upgrading for improved exhaust performance, our selection includes both direct-fit converters and performance bypass kits built from high-grade stainless steel for strength, corrosion resistance, and durability.

What Do Catalytic Converters & Bypass Pipes Do?

A catalytic converter uses a fine mesh of precious metals to trigger chemical reactions that break down pollutants. The bypass alternative eliminates restriction in the exhaust flow, improving performance in non-emissions-controlled environments such as track driving.

Core Functions:

  • Converts toxic exhaust gases into environmentally friendly emissions.
  • Maintains exhaust back pressure for engine efficiency.
  • Reduces harmful NOx, CO, and HC emissions.
  • Supports smoother engine performance and throttle control.
  • Bypass versions enhance exhaust flow and improve power output for track cars.

Upgrading to a performance-grade system ensures your Porsche continues to meet emission requirements — or achieves greater flow and responsiveness for motorsport applications.

Why Do Catalytic Converters Fail?

Catalytic converters are exposed to extreme heat, unburnt fuel, and contaminants — all of which can degrade their performance over time.

Common Causes of Failure Include:

  • Carbon or oil buildup blocking the internal honeycomb.
  • Thermal damage from overheating or rich fuel mixtures.
  • Physical damage from road debris or misfiring engines.
  • Corrosion due to moisture and exhaust condensation.
  • Age-related wear reducing catalytic efficiency.

A failing converter can cause reduced engine power, poor fuel economy, rattling sounds, or a check-engine light. Replacing it restores emissions compliance, performance, and exhaust efficiency.

Why Replace or Upgrade with Precision-Engineered Components?

Replacing a failing converter or upgrading to a bypass pipe ensures your Porsche maintains peak performance and reliability.

Key Benefits:

  • Restores optimal emissions performance and efficiency.
  • Improves exhaust flow and throttle response.
  • Reduces engine stress and fuel consumption.
  • Durable stainless-steel construction for longevity.
  • Direct-fit compatibility for Porsche 911, Cayman, Boxster, Panamera, Macan and more.
  • Performance bypass options available for track and tuning applications.

Whether you want emissions compliance or maximum flow for competition use, our parts deliver reliability, precision, and performance.

Highlights:

  • Direct-fit catalytic converters and bypass pipes for Porsche models.
  • Precision-engineered for optimal flow and reduced emissions.
  • Built from heat-resistant stainless steel for durability.
  • Bypass pipes for performance tuning and track applications.
  • Restores power, efficiency, and exhaust sound balance.
  • Available for classic and modern Porsche vehicles.

You may also like
Popular Models