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Custom Downpipe Kit for i.a. Audi S4, RS4, A6, A6 Allroad C5 with 2.7 BiTurbo engine unit and the stock power of 265-381hp.

You can choose between De-Cat Downpipe and a Race Cat Downpipe (100 CPSI / 200 CPSI).

Every part of this racing focused downpipe replacement is produced using CNC technology and is fully made out of Acid-Resistant Steel. It doesn’t include the Catalytic Converter (CAT) and thereby significantly reduces the back pressure which leads to faster spool, an increase of power and more aggressive exhaust sound. The Sports Cat version also offers huge flow improvement over the stock catalyst, which is the cause of very significant flow resistance. The bigger the diameter of the downpipe, the easier and quicker the turbocharger is able to lead off the exhaust gas. The design of the MuchBoost downpipe is optimized for minimization of variances in cross section area in order to get smooth exhaust gas flow and top performance.
Because a downpipe connects a turbocharger and the catback exhaust, its upgrade is often required for the upgraded turbo to unleash its full power. This upgrade ensures your turbo’s potential is not wasted, it is also a great choice cost-wise!

The downpipe fits to automatic transmission cars with an old type flange – 8D0253115F. It doesn`t  fit to manual and automatic transmission cars with a new type flange – 4B0253115A.

Most important features

1. The downpipe parts are CNC produced, ensuring precise, high quality elements.
2. The 2.5-inch (63.5mm) pipe diameter.
3. Removed Catalytic Converter, there is also an option to put race cat for this downpipe!
4. It is made fully out of Acid-Resistant Steel to ensure long life despite being exposed to toxic exhaust gases.
5. There are 2 sockets for lambda sensors on the assembly.
6. The shape and mounting points fit with the original car parts, no additional work is needed!
7. Clean, strong and attractive welds, inside and out!
8. 100% Plug and Play
9. Limited 2 years warranty
10. ECU tune is necessary to avoid the Check Engine Light.

Performance advantages

1. Lowers exhaust temperature, so the charger and the exhaust manifold are more protected.
2. The highest levels of performance and greater reliability under constant high load conditions.
3. Allows for smooth flow of the exhaust gases, giving your engine extra power, as well as sharper throttle response!
4. Lighter than OEM.

Compatible car models

AUDI S4 B5 2.7 BiTurbo 2000 – 2002 265HP
AUDI RS4 B5 2.7 BiTurbo 2000 – 2002 381HP
AUDI A6 C5 2.7 BiTurbo 1998 – 2005 250HP
AUDI A6 C5 2.7 BiTurbo 1998 – 2005 230HP

It is compatible with engines: AZB, AGB, ARE, AJK, ASJ, AZR.

You might also consider

2.9TFSI Hybrid Twin Turbo Upgrade Audi RS4 B9, RS5 F5, Porsche Panamera 2.9 II

Catalyst information

For downpipes without catalytic converter or with 100/200-cell catalytic converter, if the second post-catalytic lambda sensor exists, the control unit may display an error message. This does not rectrict driving operation, because first lambda sensor is present for the motor control. The second lambda sensor is only used to monitor the catalyst’s effectiveness, and this check can be programmed out through modifying the chip’s software.
Most of the cars up to Euro 3 Emissioncode do not have post-cat sensors, therefore require no adjustments to avoid the alarm.
In case of catalytic converters, the washcoat content is significantly increased and has a very high oxygen storage capacity. This means, that errors can be avoided. While the EOBD Catalysts are tested up to Euro 4, their durability and use up to Euro 6 is given.
In case of Euro 5 and 6 vehicles, a catalyst with ECE selection is needed, to avoid the above points.
MuchBoost sportcats run a 100 or 200-cell high flow cat which passes road legal emissions tests, while de-cat pipes are for RACE USE ONLY and are NOT road legal.


We need usually ~ 14 working days to perform and send this KIT.


DE-CAT, 100 CPSI, 200 CPSI

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