LS1 Swap fuel pressure dropping????

[sledge33]

just got the ls1 in my Camaro but I am having fuel pressure problems.i put a fuel pressure gauge on the car and when the fuel pump is cycled the pressure goes to 40lb but when the pump shuts off the pressure drops to 0lbs instantly.i can cycle the key 2-3 times and the car will start but been pulling my hair trying to figure out what the problem is.
I have a tanks inc tank with intank pump.it has a corvette filter that sets fuel pressure.return also comes off the filter.from the filter it goes straight to the rails.any ideas are greatly appreciated thanks jeff