Doing LS swap 2006 LQ4 4L80e. The engine starts up right away and then dies. Seems to be fuel pressure issue. If I spray carb cleaner into intake it runs for 5-8 sec before dieing. When I turn the key on it primes for 3 seconds to 60psi and it holds tell i try to start it, then fuel pressure drops to 40psi and continues to droping from there. Changed regulator same problem. I'm at a lose. Any ideas would be greatly appreciated

 

Have you deleted the Vehicle Anti Theft System in the PCM operating system tune? Sounds like VATS is still active.

Rick