Lights flicker and gauge jumps around???

This sounds like interaction caused by the MSD. There are articles here and there about this. The MSD and other high power ignitions similar to it generate so much energy, that they can "false" trigger THEMSELVES causing misfires, backfires, etc. If you look on the MSD site, there are articles about that. Here, this is known by a few names, EMI (electromagnetic interference) is one.