did an engine swap from a 2wd to a 4x4 and now the engine will not run. its a 318 tbi, ran like a top in the other truck. it will start sometimes and when it does it will run for about 40 secs and then the injectors quit and the truck shuts down. the only way to keep it running is if you are revving it keeping it in high rims, as soon as you let off it dies. new fuel pump, fuel filter, plugs, wire, rotor button and cap. it has good fire. I'm all out of ideas and any advice would be appreciated.

 

Not knowing any other info... Will leave this generic.
Check The Idle Speed Motor setting's
Check the Idle Air Control
Make sure the Run Signal is not dropping out after it runs.