gt loses fuel pressure after initial prime cycle

Whats up guys im new into this forum and the stang world at that. i have a 99 v6 with an 02 4.6 swap. I also have pats bypass and evrything over from the original donor car (02 mustang) including all wiring harness (engine and cabin).

The issue i seem to be having is at intial start-up fuel pressure is at 40lbs when ignition switch is open. Then when i turn her over it starts up then immediately there is no fuel pressure afterwards and it stays on for about a couple seconds before it dies out. I know its not the pats. because i return it back to stock on the sct tuner and it just cranks and never turns on.

Can this be a fpdm issue or ccrm issue? any ideas?

Any insite will help....

What is the fuel pressure as reported by the PCM after start up?
*How would i go about in measuring that off of the pcm; I have an sct sf3.

What is the measured fuel pressure after start up?
*After startup, it seems to me like fuel pump never turns on. Car stays on for a couple seconds on the initial 40-42 lbs it gets from opening the switch. One thing i noticed after two or three trys i have to open and close the ignition switch a couple times to get fuel pressure back to 40lbs before the initial startup crank.

Are there any DTC codes?
* Only Code i have is p1000, i have the vehicle open header until i get my x pipe in.

Do you have a set of wiring diagrams for your car?
*I do not...

YEA i would apreciate any help