Fluctuating AMMETER/VOLTMETER (MAD)

Many have. The Vreg controls to its "sensed voltage". That routes thru the key switch on the dash. If you have voltage drops thru the firewall connector, Vreg will keep increasing the alt output until it is satisfied, by getting the desired 14.3 V at the IGN1 line. Problem is it might have to boost the alt output to 18 V to make that happen, and that will be driving most of your accessories like headlamps.