The first thing you need to test for is if its lacking fuel or spark when it stalls.
By FAR the most common failure is the electric fuel pump inside the gas tank.
Rent a pressure gauge from a parts store and verify the fuel pressure.
Pull a plug wire off and install a spark tester (cheap to buy)
If you can tell me which type fuel system it has (TBI or CPI) i can give you the pressure specs. Also if you know the 8th digit in the vin # XXXXX would help me.
If you have an Autozone parts store,,,they will loan you a tester for free.
Another issue they had was the connector to the wiring for the fuel pump gets carroded and developes high resistance when warmed up and slows operation of the pump. Chack the connection back by the pump to be sure its real clean.
Make sure you are buying an OEM pump from the dealer,,,,,ALOT of aftermarket pumps are way substandard.
This definatly sounds like the typical GM fuel issues that were SO common on these vehicles.
If you can obtain a fuel pressure reading at the time of the stall it will confirm this.
That pressure is too low,,,,the system REQUIRES a very specific pressure of between 54 and 64 psi,,,if its only low by a few psi,,,it wont work right and cant open the injectors. See below.
Check that wiring
Click here to view fuel pressure info
If you have further questipns feel free to reply
Thanks for asking, and best of luck my friend!