Well, it turns out I do indeed have alternator whine, but I also have it without the sub amp.

In fact, irritatingly enough, it isn't a GLI, it is power line noise from the nav unit.

Anyone have any thoughts on how to filter our the noise? I know I can get a 10A filter for the tuner, but don't know what to do with the 40A / 80A amplifiers...

Doug