A leak/air entering in the fuel line will also cause low fuel pressure. On my old Duster mine was back by the fuel tank and the hose didn't leak fuel. It gave me fits for about 3-4 weeks before I figured it out.

1970 FE5 Duster 360/904/3.91's SOLD 1973 TB3 SpaceDuster 340/4spd/4.10's SOLD Moparless for now but when the opportunity is right I'll have another one.