low fuel pressure

I have a 96' blazer 2 dr. I am having trouble with it not wanting to start every once in a while it will usually sputter but has trouble firing. I checked fuel pressure and found that it is only at around 44 psi so i changed filter but no change. The check valve to check fuel pressure comes before the regulator to my understanding so I was wanting to ask if it was possible for the regulator to still affect fuel pressure at that point? I'm assuming it must be faulty but would like other oppinions. Btw when it does start, even after rough starting, it runs very smoothly with no problems and I can stop somewhere come back after a short time and it will start right up no problems.
Thanks, Wade

Fuel in the line is under pressure from the pump, past the injectors and up to the regulator outlet. Spring pressure on the regulator diaphragm closes the outlet passage inside the regulator allowing fuel pressure to build. When fuel pressure overcomes spring pressure, the regulator opens the passage and the excess is sent back to the fuel tank through the return line.

Key in the RUN position, engine off, fuel pump running, pressure must be 60psi to 66psi and remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. If fuel pressure drops below 55psi, one of the causes could be a leaking fuel pressure regulator. The fuel pressure regulator is a very simple design and has very few problems. Most of the time when regulators are replaced, it's a result of mis-diagnosis.

Small update I went out today to test fuel pressure with intent of checking while blocking the line to see if the pressure gets up to 70's or so to test pump but before so I checked regular pressure with engine off and it went up to 50psi this time. Im not sure if that means anything significant or not but I guess I'll know soon enough anyway.

Fuel pressure must be 60psi to 66psi. Your next step is to check fuel pump output capability. If you restrict or block off the return line, don't let the fuel pressure exceed 75psi or the diaphragm inside the fuel pressure regulator can rupture, requiring a new regulator. The safest way to check pump output, (without damaging the regulator) is to modify the pressure tester so you can connect it directly to the fuel line at the fuel filter. Post your results.