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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

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DISPLAYING 1 to 5 (of 5 products)
EXHAUSTKIT34
Product Information
Product Information
Sports Exhaust + 200 Cell X-Pipe Ø55mm Sports Cats Package

designtek

DesignTek 996 Stage 1 Performance package. High Grade stainless steel exhaust system for Porsche 996 1998-2004. 14 - 16 gauge T304 stainless steel.

Includes sports mufflers, 200 cell sports cats giving that you can really feel and superb sports car sound.
Fitting clamps in the images are not included

PLEASE NOTE THESE CATS MAY REQUIRE A REMAP TO ENSURE NO DASHBOARD LIGHTS - Please contact us regarding this!

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Related, superseded, cross reference or alternative numbers for comparison.

EXHAUSTKIT34
3606009602
3606109963
99611112257
99611113254
99611198404
99611113274
99611113275
99611113270
99611198405
99611113168
99611198504
99611113174
99611113175
99611113170
99611198505
99611112157
99611113154
99611111350
99906402601
90007428702
90008308000
90012305020
N0138322
99908405202
99711152000
99611110800
90037818301
90037810501
90038000501

The product you are viewing cross references to these numbers
99611112108
Product Information
Product Information
Exhaust Catalytic Converter Bypass Pipes

designtek

Fits:
Porsche 996 GT3

2ND ARY CATALYTIC BYPASS PIPES
More power and sportscar sound
More power on 996 GT3 +12HP
more sports car sound
Saves 30lbs 15 KG from rear of your 996.

Not UK MOT appoved

*A re-map to the ECU may require when fitting these cats.

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.

99611112108
99611112108
99611302193
996113021EX
99611302197
996113021FX
99611302293
996113022EX
99611302297
996113022FX

The product you are viewing cross references to these numbers
99711152000/1
Product Information
Product Information
Exhaust sleeve catalytic converter to silencer.
Connecting sleeve from cat to rear silencer.
Price is for each sleeve.

oematch

Fits:
Porsche 996 1998-05 (not Turbo and GT2)

Porsche 997 2005>> (not Turbo and GT2)

Porsche 991 Carrera C2 3.4L (350Bhp)
Porsche 991 Carrera C2S 3.8L (400Bhp)
Porsche 991 Carrera C4 3.4L (350Bhp)
Porsche 991 Carrera C4S 3.8L (400Bhp)
   Fits cars with and without sport exhaust

Click 'Zoom in' for large parts diagram.
Diagram ref no 13



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Related, superseded, cross reference or alternative numbers for comparison.

99711152000
99711152000
99611122002

The product you are viewing cross references to these numbers
99711152000/2
Product Information
Product Information
Titanium (grade 5) Exhaust sleeve catalytic converter to silencer.
Connecting sleeve from cat to rear silencer. Price is for each sleeve.

rohler

Fits:
Porsche 996 1998-05 (not Turbo and GT2)
Porsche 997 2005>> (not Turbo and GT2)
Porsche 991 Carrera C2 3.4L (350Bhp)
Porsche 991 Carrera C2S 3.8L (400Bhp)
Porsche 991 Carrera C4 3.4L (350Bhp)
Porsche 991 Carrera C4S 3.8L (400Bhp)

Fits cars with and without sport exhaust
Grade 5 titanium is resistant to salt water and variety of corrosive media temperatures below 300°C

Click 'Zoom in' for large parts diagram.
Diagram ref no 13



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

99711152000
99711152000

The product you are viewing cross references to these numbers
100390100392
Product Information
Product Information
Lambda Sensor Blanking Plug and Receiver Socket Set.
In case you need to relocate your existing lambda probe because it's not in the right location. Welding and cutting specialist required.


Fits:
Many Porsche vehicles. Universal kit.

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

100390100392
100390
100392

The product you are viewing cross references to these numbers
DISPLAYING 1 to 5 (of 5 products)
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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.

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