did an engine swap and now the engine will not run. its a 318 tbi, ran like a top in the other truck. it will start (sometimes) I can hear the fuel pump kick in and I can see the injectors squirting fuel, truck starts for about 40 secs and then the injectors quit pumping fuel 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.