The FPR is designed to provide lower pressure when the engine is under vacuum, and to increase pressure linerly in direct proportion to the decrease in vacuum. So when the engine is at idle, the vacuum is greatest and the pressure is lowest. As the throttle is opened, vacuum falls and the fuel pressure increases. The idea is to provide more fuel under load. The FPR can fail by either not providing enough, or providing too much pressure. Hook up a gauge to the fuel log and check a manual for the specs. You will see one value with the vacuum hose disconnected (43.5 psi for my 93) and a residual value 30 minutes after the engine is shut off (about 15 psi, I think for my 93). You should not unhook the vacuum hose while the engine is running. One way the FPR can fail is to allow fuel to be sucked though that vacuum hose into the manifold. If that's your problem, you could be spewing it all over your running engine - a recipe for disaster. Turn off the engine and pull off the hose and check it for any trace of gas first.