OK, good to know - if noise persists, radio end kit, but pull fuse on any Class D amps nearby first.

Congrats on beating this thing!
Usually the twisted pair audio lines in a BMW are resistant to acting as an antenna... I suspect that the amp might have been being picked up by PCB traces.

But good work!

__________________
musicar northwest, portland oregon

musicarnw.com

The West Coast BMW audio experts