High pitched whine using stock head unit / aux input?

[enkid]

If you have the device into both the Aux audio input, and to the Aux power socket, then try unplugging the power and see if the whine goes away.

If it does, there is a difference in potential between where the Aux power jack is grounded, and where the the audio jack is grounded, and current is flowing through the shield braid of your audio cable, and that current causing the whine.

The grounding kit mentioned earlier would help. Running a 12 or 10 gauge cable from the radio chassis to the the same bolt the power socket gets its ground from would help too.