Resurrecting an old thread. Got my F80 comp with MPE back in May, noticed some buzzing on startup. Only mod was Fabspeed midpipe installed by original owner.
Initially didn't think much of the buzzing on cold start it but eventually started looking at on forums. Initially suspected tips, then valves. Finally got around to making service appointment thinking it was going to be issue with valves but on video it seemed to be quite external as below.
When I took it in, the techs at BMW dealer sent me this, apologies for potato quality - had to screen grab from phone since I couldn't direct download.
Seems much like Sancho, Fabspeed mid is up against body/heatshield. Will likely need to bend away. But BMW also suggested this was causing slight misaligntment of MPE to cause buzzing against diffuser.
Not sure if I can bend the portion of heatshield away where it's closest by transmission or not. But I suspect it also explains the low rev rattle on throttle application in low gears.
I think next thing will be to loosen all bolts and see if I can reposition the exhaust to left a bit? Anyone else have any insight or experience?