I think you should add this under Accessories:
PAC SNI-1/3.5 Noise Filter - Ground Loop Isolator
http://www.crutchfield.com/p_127SNI135/PAC-SNI-1-3-5-Noise-Filter.html?tp=2653
I installed AuxMod like 2 years ago and have just been dealing with the ground-loop problem. I ordered this yesterday...