Looking for 2006 HHR's with OnStar. Anyone experiencing what sounds like an alternator whine / whistling noise from speakers only when using OnStar ? The noise is affected by pressing on accelerator, goes away when OnStar call is ended.

I had a similar problem with my 2007 HHR when listening to the XM radio. I had the dealer replace the sending unit on my drive by wire throttle control and that fixed it. Simular to what you mentioned I noticed that increasing throttle increased the whine, this happened even with the engine not running, but the key in the on position.
Hope this helps.