1996 Chevy Express Engine Stalling and hesitating

Engine Performance problem
1996 Chevy Express V8 Two Wheel Drive Automatic 120K miles

I purchased the Van a year ago and right of the bat the Fuel pump went out. Had a new GM fuel pump installed. Went on a 2000 mile trip up to Colorado and back with a full load. No issue on the way up, but on the way back during the drive the engine hesitated while we where going down the Freeway @ 65 mph, but never stalled. When we finally made it back into Phoenix we hit some stop and go traffic and once again we were in the fast lane doing 50 mph when the engine shutoff. It started right back up and I made it home, but the engine was acting as if it wasn't getting fuel. The engine check light never came on, I am assuming that no codes would be present. I noticed when I backed it into the grauge it smelt like their was a gas leak or the engine was running rich. I checked the tail pipe and it smelt like a very strong fuel oder. I also checked for leaks and a clogged air filter, and I found no leaks and the air filter was fine. I thought maybe the O2 sensors were acting up, not sure how to check and also some friends mentioned the charcol canister check valve and maybe a fuel injector stuck open. Any ideas on what to check?