Product description: The HPerformance 4 inch 101.6mm downpipe comes directly from the development of our 1/4 mile vehicle to series production. It is the first downpipe in the world to be consistently built with this pipe diameter. It begins at the turbocharger outlet and thus replaces the standard pre-catalyst. With this version of the downpipe there is an extreme change in sound/sound improvement, as both catalytic converters and OPF filters are omitted. The pipe diameter reduces the exhaust gas back pressure by up to 30% (depending on the boost pressure, the turbocharger and other peripherals) and thereby massively reduces the engine's tendency to "knock" on cylinders 2 and 3 - which is the case at the latest with 700 HP on 102 octane and 820 HP on E85 begins. During our turbocharger development, we were able to determine several times that the difference between 3.5 inches, i.e. 88.9mm, and 4 inches, i.e. 101.6mm, even with a downpipe directly onto the floor of the vehicle, is up to 20HP and 25NM as well as a reduction in exhaust gas back pressure by up to 0.15 bar resulted. These advantages are now also available for the street, as the downpipe has made it ready for series production. Any change to catalytic converters (replacement, change of cells or size - different from the original condition) requires a software adjustment to the engine control unit. With our remote flash solution, we also offer suitable tunings for the DNW 2.5 TFSI. In combination with the Lambda and OPF simulator box, this downpipe can also be driven without tuning. Please Note: Any of our items are not deisgned for beeing used street legal. Products that are street legal are marked as such. The offered items are for racing application only and must be installed by professional workshops with corresponding know how. If you want to install the parts on your own, please inform yourself up front, if you are able to handle the installation. You can also ask our technicans on the phone. We cannot take back items that have been incorrectly installed.