91 2600 engine issues

   Hey guys
I have a buddy who just bought a 91 b2600 2wd.  The truck is fuel injected, and its having some issues.  The truck starts up fine but after about five minutes it dies.  If you let it sit for a few minutes it will start up and run completely fine.  The previous owner had the engine rebuilt.  Could that have anything to do with it?  Any suggestions would help.  Thanks

could be fuel pump is not keeping enough pressure in the injection - could be vapor lock - could be the rebuild?  who rebuilt it?  reputable?  when it runs does it sound good, does it look clean no leaks etc?  this really sounds like more of a fuel pressure issue than a engine issue as fuel injection needs the proper pressure to keep the fuel rail full, you start it and it runs a bit, runs out of gas in the rail and the pump cant keep up the pressure, wait 5 minutes, it caught up, it runs a bit and dies again..

could be a few things from my exp with the 2.6.     Computer, distributor, main relay, coil.         If this truck is still stock check the fuel pump connections and give it a tune up also.   

Thanks guys.I will let him know