First thing I would check, the easiest is use a volt meter to check for AC. voltage 'bleed'. Connect a multimeter to your battery, turn the dial to AC - see if there is any AC voltage registered with engine running If so stop, replace alternator, check. If no AC voltage is observed, remove the drivebelt that spins the alternator. Start the engine, rev it and see if the noise goes away. If it does, again replace alt as the brushs may be worn causing arcing( internally).

If it does not - most likely option is ignition related if the whine is relevant to engine speed.

zero doubt..grounding issue.

wait..isnt there a resister at the alternator that shields the radio?

Just trying to make sense of why it is more audible when you are decelerating, is it possible that your car has one of these intelligent alternator controllers where it goes into higher charge rate when decelerating? try putting your battery on a charger for a while and then go for a drive and see if it is as bad.

Check and clean battery terminals? How old is your battery?

Battery is brand new, 2 months old. I really hope its just the grounding strap off the valve cover because it driving me nuts, much more then liberal radio:D

Thanks for the help, now I have some trouble shooting to do this weekend. If you can think of any more, don't be shy and let me know.

Yep, I can't figure it out neither? I have never heard of those controllers, good to know

Most modern cars have the charging system controlled by the ECM. Depending on the manufacturer, to what end is that task. BMW does kick in high charge rate to aid in engine braking on long descents. Again 2 easiest ways to see if the alt is the contributor A) check for AC voltage B) disconnect drive belt; run and or drive it short distance to see if the issue goes away.

I have no idea why I assumed you have aftermarket sound. maybe when I saw you checked a ground lug.

If that's a factory radio and no amp, radio internal ground is likely burnt.