check this out
basically a muffler delete but keeping the quad setup...
http://www.1addicts.com/forums/showthread.php?t=783926
Edit: Dont know if the hartage quad and the iCarbon have the same positioning for the pipes. Might have to do some research on that...
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2010 AW/BLK 135i VM 6465 Single Turbo, JB4 + MHD, VRSF CP & Tial, Big Tom, Fuel-It PI + Stage 3 + Return + Ethanol Sensor, BMW PE, MFactory LSD, Spec 3+ & MFactory SMFW, RB External PCV
Best stock turbo 12.5 @ 19.46 spinning all the way down 
RIP 
2008 AW/BL 135i