1997 Ford F-150 fuel pressure

I have just tested the fuel pressure on my pick up. The pressure should be 55psi when ignition is on and 55psi when vehicle is running.

Currently when the key is in on position the pressure is at 32 psi. When running it is 32 psi.

When I rev the engine the gage rises to about 37-38 psi. 5 psi increas.

I also removed the fuel regulator vacuum line it jumped about 5 psi.

Note: I pinched the the fuel return line and the pressure jumped to 60-70 psi depending on how long I pinched the line (up to 5 seconds). Also, when the vehicle sits for about 20 min with the pressure gage still hooked up the pressure rises to 38psi.