Yeah, I tried a mechanical on the port engine, and it failed due to vibration. Part of the maintenance is going to include some mechanical gauges I can count on. I don't think it's electrical. Especially given the AF content in the oil. I pulled the pan, regulator and oil pump a few years ago, and found some crap. It' got to be jamming up the regulator.
The indicator for this engine has always been a bit jumpy. I've heard they are notorious (Detroits) for odd oil pressure indications.