It seems whenever I put a fuel pressure gauge on the Schrader valve, the needle wants to fluctuate all the time so I cannot get an accurate reading. I'm thinking the fuel pressure regulator is bad as I'm having some stomach issues. Most of the time it's at low speeds period usually 30 miles an hour or less. With the key on, the PSI is at 38 but drops to 10 PSI in about 40 seconds or so. So it doesn't hold a constant pressure for any amount of time. The fuel pump is an original AC Delco that's only been in there probably 5 years. Fuel filter has been changed about 4 months ago. It's either the regulator bad or the injectors one. Does anybody know why the fuel pressure gauge is fluctuating?