Here's a clip of some of the noise I'm getting, this is with the audio turned off too:

https://www.youtube.com/watch?v=8dpAAkG8vIg

Car is a 2003 530i w/ DSP - added OEM Aux input when I first bought the car like 6+ years ago. Noise started this summer, and I replaced the subwoofers and rear parcel shelf speakers (still using OEM wiring harness). Noise continues.
It'll do this intermittently, sometimes constant, sometimes it disappears.

Is there a method for testing the stock amp? Also, as a side note, I think the car may have had an OEM CD changer in the trunk, because there are 3 wires in the Amp area that aren't connected.