Thanks for the help. I'll check things out with a multimeter. Incidentally, the power interruptions do happen while the engine is running with the diode in place. Once things work well with the engine running, I'll be more concerned with how it works with the ignition in accessory mode.

I have 12 gauge wire running directly from the battery's positive terminal to the Empeg and my Amp. Factory wiring is only used for the ignition signal and light sense signal. Empeg and Amp are grounded to a common spot on the chassis with 12 gauge wire as well.

-Ryan.