1995 Chevy Blazer Car stalling

My Blazer has always had issues with the EGR value and carbon deposits, which would cause the check engine light to come on and the car would run very roughly. But, about 4 months ago, the car started stalling out when driving at normal speeds. The lights on the dash would light up, and you could full an abrupt loss of power. In a few seconds it would just start itself back up again. When stopped at lights, etc, I'd have to rev the engine to keep it from dying. At that time, the shop replaced the plugs and wires, and it ran great until about a week ago. Some days it runs great, other days it has this exact same problem. The check engine light has gone on and off quite a few times, but the last time I took it in, the shop says it isn't saving the code.I'm wondering if that may be clue - maybe a computer problem or wiring? But, this morning the light came on again, they hooked it back up right away, and said there was a code that had to do with the O2 sensor, but they don't seem to think that it's the issue. Coworkers have suggested the fuel pump, but the shop has checked the pressure and they say it's okay. Please, help!
Thanks,
Ruth