91 s10 stalling/sputtering when warm

[save_me_jebus]

I scanned through a few other threads similar to my problem but didnt find much to help. Heres the situation

A 2.5 L S-10 came into work today, the symptoms were when ever it warmed up it would stall out.

First thing we did was check out the MAP sensor, Seems good. So we moved onto the EGR valve, it was leaking but we fixed that... Still no good. So then we busted out the OTC scan tool to see whats happening, and i noticed that on the O2 sensor it was flicking between open loop and closed loop and the voltage was going to about .90 volts when rich, down to 00 when lean, when it gets to 00 it usually either sputters like a mother fucker or stalls out.

What voltage should the 02 sensor run at? I think i rememberd in school that it should sit at around 5-6 volts? So we puled that one out sure as shit it was white and cracked, well we found a used one in the shop and through that in, it seemed to improve a bit, it now only coughs when the voltage gets low, rather than die. I was thinking it could still be the 02 because we used an old one, it coulda been dead or dropped at one point and still faulty.

So then we checked fuel pressure and it was exactly what the book said, 9-13 pounds.

All 3 of us are rackin our brains trying to figure out what the fuck is up, possibly plugged exhaust? blown computer? ( my boss says the comp is acting slooooow)

If anyone has annnnnnny more ideas Throw them my way cause we're fuckin stumped.

[DetroitMuscle]

If the voltage is dropping then you gotta find the source of the draindown Is there a short anywhere? bad ground? alternator going bad maybe?