I have a Mark IIa and I am going to try moving the Becker ground out of the harness tonight.

I would point out that the factory CD changer (made by Sony for Becker for Porsche) mounts in the front trunk and is connected only to the head unit and to no other grounds anywhere in the car. This system has motors, processors and serial data all living together with no noise, that I am aware of, reported over the last 5 model years.

It seems possible to make a system that truly does isolate the audio.

I will report on results of rewiring later. Thanks for all of your input. I have identified at least four Boxster S/Empeg installs here so perhaps we can find a viable solution jointly!

Lynn