Plesse help, truck won't stay running.

[Sooner84]

Alright so started adjusting some things in the tune and was almost done. We wanted to fix the idle surge and hiccup upon initial start up. Got the idle better but not perfect. Once we started addressing the start up it only got worse and worse, to where it would start but wouldn't stay running at all. Loaded back the tune that was on the truck before we started adjusting and the same thing. Would not stay running.

Details on motor, 5.3 with 100kish miles. Ls6 cam, longtube headers, cai. Nothing special.

First thing we think is its not getting enough fuel. New fuel pump and same issue. Getting pressure at the rails, getting spark, relays and fuses are good, its not throwing any codes, I swapped mafs from my other truck and that didn't change anything, Any ideas to what's going on here..? Also while he was tuning it wouldn't allow him to get to the timing.

I changed the cam position sensor with one I knew was good from a 5.3 we had in the shop. Now it starts but its just as crappy as before, the colder the weather is the more cranks it takes to get it running. When I get it running I have to feather the throttle for a while for it to get up to idle.