Air pressure in fuel lines?

My 90 pontiac 6000 3.1mpfi is doing something weird, when you start the car it takes a few seconds to start *nothing major* it starts fine but has a roughness to the engine. I turned the car off after messing with it for a couple hours.. 2 hours later I return and hear a hissing noise under the hood. I find the fuel pressure tester valve to be the culprit, I push the pin down to see if it was just out of alignment and I got a literal geyser that shot out of the valve that hit the under side of my hood and arched a good 3 feet past the front of the car. I took off my gas cap to relieve pressure and had the same thing. I d/c the battery thinking the pump might be boiling the fuel and let it sit for another hour.. come back to same results, releasing the pressure and letting it sit 10 minutes gets the hissing again. When fuel comes out you can see its loaded with bubbles. Fuel pump was replaced 6 months ago and I have a spare fuel rail with regulator and injectors.. swapped in, same prob