Had same problem; P0171 and P0174;Low fuel pressure: only 17 psi and it should be 60-70 psi; changed pump still got only 17 psi. Took down the tank (again) and put the gauge directly on the output pipe. Still only 17 psi. I extracted all the bolts holding the pump assembly and fed 12 V to the black and red wires in the harness. With a flashlight peering in, I lifted the assembly just enough to see the top of the actual pump and I saw that the regulator was spewing fuel from fatigue cracks all over the black plastic housing. These cracks were microscopic and virtually impossible to detect without it actually running. (This can be very dangerous especially if you're a smoker, duh) Voila I found the problem. Now how can I get a regulator/housing without buying the whole assembly? I don't need a pump. So I looked at the regulator and saw that the regulator (not its housing) itself will last forever, it's just that cheap plastic housing that's bad. The pull-it yard I went to had a few explorers but all 3 that still had a tank had tanks that were inaccessible--no wheels, laying on mud, and no they ain't gonna topple the car for a regulator. So I made a housing out of copper pipe and brass fittings and a propane soldering job. 62 psi! Now, it'll last forever.
