Did you ever dyno before and after to see for any gains or losses?
Aside from the pure sound, how does the car actually feel now? Everything I've read and seen shows massive loss of low end torque, much like BW's 3.5 race exhaust, but gains are to be had up top.
02 Carbon Black M3 6MT
456whp/312wtq @ 8psi, No #'s yet at 9.5psi
4.10 / Headers / ESS VT2-550+