I just got mine installed today, I do not have a CEL after 30 miles.
Here is a video clip, of both my M5 and BM5BULLIT's
My M5
BM5BULLIT'S M5
This is a video of my M5 before AMS Downpipes:
Keep in mind this was taken on a normal microphone, so you can't hear everything. You can definitely hear the turbo, and the sound is amazing. Completely (in my opinion) wakes the beast up.