Greetings!

I have similar alternator noise problems (typically only with significant load, AC or electric heat / defrost), but I have the same noise filters you are talking about. I tried grounding them, but heard absolutely no difference in the sound. I think you are on the right track with the grounding, but I do not have enough experience to advise you on this.
_________________________
Paul Grzelak
200GB with 48MB RAM, Illuminated Buttons and Digital Outputs