Fuel pressure dropping while driving and under acceleration to zero at idle runs 4 lb electric Blue

Okay, here's a recap. First Holly blue fuel pump with stock plumbing configuration could be regulated to 5 and 1/2 PSI. But as the RPMs went up it would drop down too close to zero but would come back up when you stop at a stoplight. So installed a new Holly fuel pump. Shortened up the line going into the pump from the sending unit. Made a direct path for the fuel. Fired it up. It would go up to 5 and 1/2 and then dropped to zero. When you take it for a drive it stays at zero. So I took the pump apart. Everything looked brand new bypass spring and piston look new move freely. So I got a moroso. Holly fuel pump spring to make the fuel pressure 19 PSI install the spring fired it up. I can only get six PSI before the regulator from the supply line from the pump. So it's either the pump or something's wrong with the regulator. I talked to fuel lab. They said that regulator is idiot-proof. It's most likely not. It. Must be the pump. Ideas or thoughts?