Darwin,

I feel your pain as I have been plagued with this problem in my Miata for 2 years!

I rid myself of the whine by grouding the sled to a different ground point than the HU

But alas it came back

Then, I rerouted my ground wires to join at one place, which was the stock grounding poing for the original HU

Alas, the noise reappeared

I tried my Empeg in another car and there was no noise so I was sure that it wasnt the unit

However, I did get rid of the whine by pressing in the upper left hand corner of the HU in the sled with considerable force..the whine went away. It does reappear every now and then but i just put a bit of pressure on the unit and away it goes.

I dont know exactly what is happening when i press in, but obviously it is closing some open circuit the make this work right!

Keep plugging away and good luck!