New to Group and new to LS motors

I joined the group hoping to find some answers to some issues I am having. I recently had an LS1 Installed in my 85 K10 chevy. After installing and getting it started my "mechanic" has disappeared and im still having troubles keeping it running after it starts.

current setup that I know of...

LS1 out of a 2002 corvette. Stock motor no mods to date.
Computer came out of same car and was taken to LSX in Alvarado, Tx to be flashed and had a bench tune installed.
Has an adapter harness, was installed by "mechanic"
Transmission in truck is a 700r4 (yes i know not everyone approves but its what i have) Tune in computer shows the trans as a manual because its not computer controlled.
Cable throttle body
Fans are currently wired stand alone
An inline fuel pump was installed with filter (deatschwerks is the brand)
installed the factory corvette fuel filter/regulator with return
Fuel pump is direct wired to a relay not computer controlled.
Manifold exhaust straight dual pipes (i was told this might be a problem, but ive never heard of it)

Ok, so now for the problem, The truck will start and idle fine for about a minute and a half, then the fuel pump starts to get louder and starts surging, if i let the surging continue the truck will die, fuel pump will build pressure and stop again, at this point i can fire the truck right back up with no issues but the process will just repeat itself. If i give the truck throttle it will run fine for as long as i keep my foot in it.

I have put a scanner on it and the only codes that come up are fan control reading high voltage (fans are wired separate) and Malfunction indicator light code (old truck no check engine light)

i am at a loss on where to go from here, only thing i can think is that tuning is a problem or i need to figure out how to wire the computer into the fuel pump. If the computer to fuel pump is the answer how do i do that. I dont have a wiring diagram and my "mechanic" has disappeared.

Any suggestions will be appreciated. Im not looking at making it a race truck just want it to drive.