Well actually this tweaking with a resistor is only for aesthetic purposes because you are not going to get an entirely accurate result regardless. Even if you were to use a calibrated mechanical gauge and a variation of resistors to adjust it you're only going to be able to dial it in at a specific point such as at cruise rpm. As I pointed out, what would be the purpose of knowing exactly what pressure you had at any given moment? The oil pressure gauges in automobiles are generally just glorified idiot lights anyway. You would never use one and record it's readings to do any sort of troubleshooting or make any kinds of adjustments. The only reason these Sunpro units are used is because, as I pointed out, it's difficult to accept the visuals of a tachometer needle at 5000 rpm and an oil pressure indicator needle on zero, even though the low pressure light is not on and you know you have pressure. I don't know if anyone has even assessed the accuracy of the original sender prior to failure either so there's really no basis for the adjustment to begin with other than where you feel you want to see the needle pointing.