Circuit Werks latest Satin / Brush Finish for the BMW 335i N55 2011-2012 Turbo 4" Downpipe. Fits all E90/E91/E92/E93 N55B30 motors from 2011-2012 perfectly with stock turbo or an aftermarket turbo using the stock V-Band Clamps. Fits all the 335i Coupes, Convertibles, and Sedans as long as it's the single turbo N55 motor. All made out of Stainless Steel and T.I.G. welded. If you have the 2011+ 135i the mounting tabs will need to be modified in order to fit. Professional installation might be required but this is a direct bolt-on. Comes with three o2 bungs with plugs, if you do decide not to use them. Might not pass smog in some States even though there are secondary catalytic converters on your exhaust mid pipes. Typical gain with a tune is around 20+ hp. We also sell CEL Fixes separately. The most restrictive part of any exhaust system is the catalytic converter. The stock catalytic converter is meant to filter the flow of the exhaust gases to reduce the amount of harmful gases into the atmosphere. That is a potential performance restrain. Downpipes eliminate the stock catalytic converters and reduce exhaust back pressure by maximizing exhaust flow. This downpipe allows the turbo to spool up a lot faster and also build boost quicker. The result brings out the vehicle's performance potential by giving it a high free flow exhaust system.Not Compatible With Convertibles