Electrical Surge/Drop

[viper5150]

I've got a 94 mustang GT and I'm having trouble with the electrical system. It seems that there is a somewhat frequent surge or drop in voltage. It's happened on a few occasions, and I'm not sure what to link it to. The battery and alternator/regulator have been replaced, so I've pretty much ruled those out. Connections appear to be good and clean. What happens is on occasion the Electrical system seems to "reboot" (for lack of better explanation). the voltmeter needle drops and appears to be powered off for about 1 second, and then returns to normal. I've also noticed that the needle is a bit "jumpy". If the radio is on, it sends a fairly loud pop over the speakers, I'm assuming this would be the amplifiers for the Mach 460 sound system powering off and on. I can't seem to find anything to relate it to, it doesn't seem to be dependant on anything like the fan coming on or off, etc... Possibly a relay switch? Any ideas would be greatly appreciated, as this is driving me crazy.

Thanks