And this thread too... http://www.1addicts.com/forums/showt...1#post12321627
Yup, it seems to be a Chinese market thing. Seems that BMW AG put a different exhaust on Chinese market 1M's - and the inside pipes do not get much exhaust flow and hence stay clean! Btw... I noticed the same thing on the new F10 M5 when I sampled one recently.
You could order a non Chinese 1M exhaust or take your off and cut out the blockage.
I looked up the rear exhaust on RealOEM.com
and low and behold... China DOES get a special different rear exhaust muffler! National China version...
China exhaust muffler #18107847100
EU/RoW spec muffler #18107845402
The curious thing is how can the 1M muffler/can pass Swiss noise regs while not pass Chinese ones!?!?