I attached a sketch that I made showing "some" of the circuits that I think were affected by the feedback.
During the RUN mode, the ignition switch feeds 12v to most, if not, all of the car circuits. This sketch shows how the RUN circuit is connected to my ammeter, the MSD ignition feed voltage gauge, and the battery voltage gauge which were all being affected.
Once I drew it up, I could see how each one was being affected and the sketch just kept getting bigger, so I stopped. My dash lights were also fluctuating but I started to run out of paper so I stopped mapping it out.
But once again, the $1 diode which comes in the kit seems to have fixed the feedback issue.