2000 Silverado Random Stalling

[mfarmdawg]

I tried a search first and didn't find what I needed....

I bought a 2000 Silverado 4.8 and Auto trans with 244K miles on it for my son's first vehicle. Everything was going well for a few weeks and on Thanksgiving Day it started randomly stalling. No pattern, not only when warm or cold, no SES or Security lights on the dash for the most part. Sometimes it will stall right after starting, sometimes it will run fine for days and then randomly stall. So far we've replaced the ignition switch, the ignition lock cylinder, fuel pressure regulator, the Evap canister, the purge solenoid on the manifold, checked fuses, relays, fuel pump pressure (stays at 50psi, drops to 46 after the engine stops and then climbs back to 51), it still has the same issue. I believe the fuel pump was replaced as well as the evap canister and possibly the vent valve solenoid before by the previous owner. The bed bolts are somewhat loose and you can see the wear spots from original install from the bed going back on. I'm at my wits end with this thing. I'm afraid for him to drive it like this and the possibility of it leaving him stranded in the middle of an intersection or causing an accident.

Please help?!