Little update: I replaced the igniter to distributor cap wire, and all four spark plug wires with new ones from Duralast from Autozone. No noticeable difference in performance, though that background whine in the speakers was still present!

Oughta get some emory cloth to clean the cap contacts inside and out and get that RF shielding and see if that will make a difference...

 

Disconnect the wires on the alternator and see if that makes any difference in your noise.

 

Will do that soon to try out. Just guessing you do that with it running?

 

Yes, it will see if the interference is an open diode making the noise.