Oops, sorry to Technic and VP about the mixup, I've corrected my post above. I guess it's been a long day!
Sorry if this is obvious ctuna, but did you mean measure the resistance between one of the ground terminals on the rca input jacks and the ground terminal of the amp (where you insert the ground cable)?
By the way Technic, I know your amp harness is not the cause of the noise. Many have used it without issue. Plus like I said, the noise was there in the OEM setup, just much less noticeable. I hope I didn't come across as implying that when I said that anything post-amp couldn't be the cause of the noise. I think at worse case, I might run a new pair of RCA wires from the HU to the amp. If I remember right, I saw somewhere that you made a harness for that connects to the back of the HU. I might contact you at some point to get one.