Here's our 135i running straight 91/methanol w/ Macht Schnell 3" DownPipes and still running the OEM catback exhaust:
Here is a list of modifications to the vehicle for this run:
2008 BMW 135i 06/08 build
GIAC Stg. 2 beta calibration
Macht Schnell 3” Catless Downpipes
Macht Schnell Dual Cone intake kit
Macht Schnell Intake Scoops
Snow Performance S2 Boost Cooler
Evolution Racewerks Competition Intercooler
Forge Motorsport Adjustable Diverter Valves for N54 Turbo