It's a BMW performance exhaust- of course it's going to drone.
Hated my BMW PE - it was raspy and sounded like a damn Ferrari coming down the block. Cold starts would give me a migraine and when it warmed up it wasn't much better.
The damn flaps are open all the time- that's the problem there's no refinement- it's like an unruly brat.
One of the main reasons I sold mine within a month and went with a DINAN exhaust.
My E92 328 PE sounded so much better.