fuel issue?

hi ya'll,
i'm having a issue with my 1992 oldsmobile custom cruiser with the 5.7
it starts and runs great but if i drive it around town doing errands it runs fine. when i shut it down, go in a store and come back to it after a short period, say 15-30 mins, it will start but rev up and down, like its fuel starved, quit running but start right up and run fine. like i said, it won't do it when its cold but, only after it runs a bit and it is shut off and restarted.
my first thought was fuel pump but i'd love some opinions before i go dropping the tank.
any help would be much appreciated!
thanks

Might be the idle air control valve on the throttle body. It's easily removed (but be careful with paper gasket) and the pintle and port can be cleaned out. Replacement parts are available and relatively inexpensive if this proves to be the problem.

The symptom you are describing is the first indication that the hose between the pump and outgoing fuel line is starting to fail. The variations in idle speed is the determining factor. As the pump starts to run, it twists the hose and the crack opens, then the fuel dumps back into the tank. The pump is no longer under pressure and rotates back to its original position and the crack closes allowing pressure to build again, and the pump again twists the crack open. This is cyclical which causes the pressure to fluctuate hence the idle variation.

thanks for the info guys.
i'll try the iac valve first since its only about 20 bucks from rock auto. if that don't do it, looks like i'll be dropin the tank!
appreciate the help.
cheers!

Similar thing happened to me except instead of reving up and down, it would die 2-3 times before starting and running good. I replaced the fuel pump and it fixed the issue permanently.