I didn't even know this existed. I was looking at building something similar as a custom a few months ago using a y-pipe and a Vibrant muffler and resonator with 3.5" piping.
'08 E90 335i 6MT. VM 6466g2 kit. Stage3+ Fuel-It with FPR return, BMS PI injection, widebody
'09 Z4 sDrive35i DCT, MHD Backend flash, JB4, DCI