RENNtech Stainless Steel Muffler for 231 - SL 550 bmw-3-series--e90-e91---2005-2012--335i-3-0-l-i6-twin-turbo--n54-n55--esr9908178 ECU Upgrade: Our proprietary tuning

ECU Upgrade: Our proprietary tuning module stores both the RENNtech tuned file and your vehicles stock file

and better sound

R2 Performance Package for the W205 - C 63 AMG includes:

9 at 3350 rpm 662

RENNtech Stainless Steel Muffler for 231 - SL 550 bmw-3-series--e90-e91---2005-2012--335i-3-0-l-i6-twin-turbo--n54-n55--esr9908178 ECU Upgrade: Our proprietary tuningRENNtech Stainless Steel Sport Muffler for 231 SL 550. Gaines: +15HP & 20TQ RENNtech stainless steel (SS) sport mufflers are hand made and rigorously tested to remove any unwanted resonances in the cabin to deliver a deep sound that keeps with the character of a luxury performance vehicle. Our mufflers offer incredible sound in a lighter than the stock weight exhaust with improved performance. This is accomplished by reducing exhaust system back