Here are some reference threads for you to review.
http://empeg.comms.net/php/showflat.php?Cat=&Board=install&Number=77207&page=1&view=collapsed&sb=5&o=0&fpart=
http://empeg.comms.net/php/showthreaded.php?Cat=&Board=empeg_tech&Number=60062&page=&view=&sb=&o=
http://empeg.comms.net/php/showthreaded.php?Cat=&Board=install&Number=56970&page=&view=&sb=&o=
You can also search for the following posters, all of whom have discussed this subject extensively:
"ClownBurner"
"Neo_to_Rio"
"sendero"
"ellweber"
My illumination dimming works fine but I had to select the proper signal from the Porsche cluster, most accessable at the HVAC control unit above the radio. Alternator whine has been successfully eliminated by a variety of means including ground loop isolators, DC-DC inverters ot isolate the Becker and Empeg grounds and gorrilla (lots of copper required) grounds between the two.
Check out the above posts in detail for more info.
Lynn