I just got my B&B Triflow installed yesterday. I just have one word abou it. WOW!!!! I mean the car sounds unbeleivable. Its phenominal in every way. LOOKS, and SOUND. I will post some pictures soon. I will also try to load up a video clip. For anyone who is thinking about an exhaust for the M5, I would greatly recomend the Triflow's. The quality of the finish is superb and the sound is like I never imagined.
I heard a lot of people saying that there is some groaning at low RPM. Its not that bad at all. The cabin sound is quite nice. Almost like stock but with some rumble. You will not be dissappointed.