sounds like a problem i'm having with a 95 monte carlo, has a 3.1l and just stalls for no reason will always start back up, i've replaced everything i can think of pcm, both crank sensors, map sensor ignition module, pcm it's not a fuel issue pressure testor holds all the time. Honestlly i gave up on the car. It's a oop (out of province car) so it's rusty i suspect a partially rotten wire somewhere. my fix i bought a new car....lol