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I just installed dual 340 pumps in October May trans am ran good , now under boost the car lost power and when I checked the fuel pressure it’s about 42 psi when I give it gas it goes to about 50 psi , I had trouble with the rubber hose that goes from the hat to the pumps b4 , I pulled the pumps back out every thing looks fine , I checked the fuses and relays they were good , is it possible that the fuel pressure regulator isn’t working?
It sounds like it might be working the way it should, A boost referenced regulator will start at a base pressure (0 map reading when engine is not running) and will drop pressure with vacuum (Engine at idle) and raise pressure with boost on a 1 to 1 ratio. So with base pressure set at say 53lbs without the car running, Under vacuum the pressure will drop 1lb for every pound of vacuum and it does to opposite under boost pressure, If you have 10lbs of boost then fuel pressure will increase 10lbs over the base amount.
Check the voltage to the fuel pump. If pressure is low at idle, and goes up with rpm's, you alternator could be failure. Or a bad connection is limiting voltage. Check it at the pump.
I replaced the fuel pumps with new racetronix’s dual 340 pumps, I bought the hole sending unit and pumps assembly from ws6 store , put it in , now I have no fuel pressure at all, I do have power going to the pumps , should I try sticking an stock fuel pump in to see if it would start?
And your fuel pressure is zero or low? Have you tried putting the pump in a bucket and provide power to see flow?
1st time I cranked it , it was low than 0 , I did pull the feed on the top of the fuel hat , off and ran an hose to an empty bucket it pushed fuel , but I don’t think it was enough pressure
Not enough voltage or a poor ground can cause those problems.
Assemble everything just the way you had it. Push a straight pin into the positive wire to the fuel pump, at that connector. Use the straight pin to measure voltage. Should be 12'ish volts with engine off. And then rise to 13.5'ish volts with engine rpm's. If it doesn't do that, then it's an electrical problem before the pump.
Push a straight pin into the negative wire. Measure resistance to ground; should be nearly zero.
With the pump and bucket removed measure resistance between the connectors on the fuel hat and the connectors on the pump. Should be pretty close to zero.
Put the fuel bucket in a bucket of water, with about 6" of water. Hot wire it directly to a 12v battery. If it still doesn't pump like it should, then the pump is bad.
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Low fuel pressure 
