Any of the experts know what would cause all the gauges on one engine of a twin setup read lower across the board? They all seem like they are off by the same margin as well. That engine is also having some ignition issues, wants to stall and run rough maybe not good spark, possibly related? Bad ground? Main ground looks ok but maybe loose or broken inside shrink wrap somewhere a possibility?

either a bad ground or one of the alternator is putting out more volts that the other..if you can get at the back of the dash try putting a jumper on the grounds and the powers and see if it makes a difference..

I am going to check and clean all the grounds. If one alternator is different in voltage how do you fix it?