If you already have the gauge they are a few things to check to get the rated psi.Keep the motor,pump,unloader and spray tip in mine while checking these things.The motor has to turn so many rpm's and the pump has turn so many rpm's to get the rated psi of the pump.The unloader has to be set and you have to have the right size spray tip in the wand.If its weak all you may need to do is replace the wornout spray tip.

When In Doubt Think It Out