great DIY and information as always dack.
I have a question. Whats the difference between this and getting a muffler shop to just cut out the secondary cats and put a small tube in their place?
2009 128i Coupe Crimson Red
MODS: -Injen Intake-Magnaflow Exhaust-Carbon Fiber Spoiler - Carbon Fiber Grilles - OZ Ultraleggeras - CF Mirrors