Here's my best attempt at a *****y video of what mine sounds like from the cabin. The whine that changes pitch with engine speed is pretty easy to hear, though you'll probably want ear buds.
Car is fully warmed-up but temperature doesn't seem to matter...this is just what it sounds like.
**edit**
Just came across an old thread that talks about it (mostly on the second page). One post toward the end of the thread indicates that the whine might actually be a wastegate thing rather than the timing equipment. I can’t decide if that makes sense or not.
https://f30.bimmerpost.com/forums/sh....php?t=1204279