Dorian is correct, the small hose that connects the pump to the sender sometimes splits and will give all kids of frustrating issues that are hard to find. Like he said, if you deadhead the pump with a pressure gauge that should be enough to let you know without dropping the tank that the hose is fine. If that hose is bad you need to realize that that hose is special hose called SUBMERSIBLE FUEL HOSE and you cannot use the standard fuel hose otherwise the fuel will eat the hose from the outside.
When I plumbed the fuel system to handle the TPI pressures I used braided hose with -6AN fittings from the tank to the fuel rail. I also converted the fuel rail to have the lines enter and exit out the back instead of the front.
I may be able to disconnect the fuel line on the engine side of the filter and see if I can get a fitting on it to get a reading.
