Milltek has an exhaust coming out. I really liked milltek's built quality and sound. I had one of their exhaust for my v8 s4.
Its $1400 tho. Heres the link if you wanna take a look.
http://www.stratmosphere.com/bmw.htm
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Previous - E90 335i, E82 135i, E89 Z4 3.5SI, Range Rover S/C, Ultra White RCF, Maserati Granturismo
Current Lexus: SMG LC500 performance package
Porsche:1973 911E
Ferrari 575 SA, 458 Italia