Why does it run and stall.

Okay, I recently acquired this car w/ a reportedly bad fuel pump. Here's where the fun begins. 1) replaced fuel pump,pick-up screen and filter.2) replaced all plugs and wire set.3) replaced TPS, cleaned IAC and MAF sensor.4)new serp belt and battery.5)new pcv valve and Alt. Most of this was not replaced/serviced as part of regular service.
Car started and ran w/ rough idle. When you accellerate to passing gear, engine revs up and dies. Start and drove car on highway and ran great. Next day started up to verify, engine runs for a few secs then dies.
I have since taken the car to a repair shop and had it for 2 days so far with not much luck on their part either. Tech states that all sensors are working correctly and show proper values. He stated that when hooked up to a particular scanner, the output on this piece, I can't remember the name, would show at 120-125mv. output. Car runs like a champ at that level but notices it starts to decline and the engine performance dwindles accordingly. They are currently looking for a possible grounding issue to see if it is related to when the trans was replaced by previous owner. I'm about to purchase a grenade and take this thing to its final resting place.