No, I know the top one is vacuum and the bottom is the fuel return.

I just removed the regulator and I know there is pressure in the rail leading up to it because there was a pop and a nice splash of gas when I pulled it off.

Does there have to be a certain amount of pressure going into the regulator before it allows fuel to go through and back to the tank? I know the FSM states that you should hear fuel draining back when testing the fuel pump with the engine off.

At this point I'm trying to determine if it is the regulator or that the pump isn't pushing enough pressure...