1990 Pontiac 6000 fuel volume test

Can I test the fuel volume output at the test port on the fuel rail? With a press. Gauge hooked up I get 40+ press. When I hit the key : the car will start eventually(pumping the pedal) will idle good but when I try to give it gas it just dies out not sure if its a fuel or an air problem could it be a pressure reulator or a mass air flow sensor, the car ran good then just quit thought it was the fuel pump, pulled it out then put 12v to it and it seemed good put it back and put a j-yard computer in it- trying to avoid towing it to a shop and those costs any suggestions