Ok, tracked down the problem to the wiring loom. Some of the rubber insulators at the base of the line outs had split. Whenever they came in contact with the sled horrible line noise erupted. I think the change in temperature as the car warms has something to do with it as well.

Schofiel: I am using a rebuilt Bosch 90 amp alternator, and a fairly new Die Hard battery. I'll try the grounding strap on the bonnet, that may help. When I get the replacement wiring loom I'll measure the voltage differential. When I finished playing with it last night after discovered the broken insulation, I had the line noise down to almost nothing. This morning I set out to work, and it was all back.

Bottom line, I'll check all those things, and get back to the board with what I find. Hopefully someone will benefit from my experience.

Btw, I think the broken insulation is also affecting the line ins. When I tried playing my MD player through them, it sounded horrible. I'm waiting for the replacement loom to verify that it is in fact the broken insulation.