Fuel Pressure?

[PKRWUD]

The fact that it bleeds down so fast is not good. It will lead to hard starts, with long cranking times.

Follow the fuel line from the schrader valve back towards the fuel tank until you find a section of the fuel line that is rubber. With the engine idling, and the gauge hooked up, have a friend turn the engine off, and at the exact same moment, clamp the fuel line where the rubber hose is. You can use ViseGrips if you don't have anything else. The purpose is to seal off the supply hose completely, instantly, when the engine is shut off. Upon doing this, observe the gauge. If the pressure bleeds down quickly, just like before, remove the vacuum hose from the regulator, and look for any signs of fuel. If you find any fuel in the vacuum line, replace the regulator. If you don't, repeat the part with your friend, and the engine running, only this time, when he shuts off the engine, clamp the fuel line where it goes from the right bank of injectors to the left bank. If the gauge leaks down, you either have a bad fuel pump, or a cracked fuel line inside the tank. If the gauge becomes steady, or leaks down much slower than before, you have leaky injectors, and they need to be replaced.