i've installed a pioneer 50 watt stereo cd player and a 30 watt power amp in my 86 gt vert. where is a good place to ground these to eliminate the high pitch whistle? i am also running an msd 6a ignition with the filter. i can't get rid of the whistle. i've read it's probably a grounding issue, but i've tried various places, and kept the grounds of the 2 units as far away as possible. any suggestions?