Just picked up a gravity fed hvlp gun at a yard sale, and was fooling around with it. On the handle it says 30 p.s.i at the inlet, it really doesn,t want to spray at that low of pressure.When I turn on the gun the pressure drops to about 15 or 20 psi, maybe I,m wrong but I feel like the pressure should be about 25-30 when the gun is on.The gauge is srewed in to the handle, anyway I,m not sure?