My wife and I have a '95 Grand Prix with around 146k miles on it. We were using it for runs to our parent's house (~250 miles) and church (~3 miles) but not much else. About 3 months ago it died unexpectedly. We could start it, but when we would try to use the gas it would just die. I found out that if I used the gas well enough I could keep it going well enough to get it back to our parking lot.
Fast forward to today. We replaced the fuel pressure regulator and PCV valve. The car idled fine but when we tried to rev the engine it would usually sputter and try to die (if we let off the gas it would go back to an idle usually). Occasionally it would take off without a hitch and hit 3-4k rpms in park. In drive we made it about a block before it died again. Car restarted after a while but needed to be pushed to get it out of the street (wouldn't go anymore).
The fuel filter is new, the air filter is fine, the oil is nearly new.
We started the car again and let it idle for a while. It did well at an idle but still wouldn't take additional throttle well. It finally died and wouldn't start again. The oddest thing was right before it died and we couldn't start it again. It would go from normal idle (~600-1000 rpms) to low (sub 500) to high (1.5k+) and then just fluctuated between dying and high rpms til it just died and couldn't be revived. My father in-law disconnected the fuel line after the fuel filter and we tried starting the car. No fuel came out. We disconnected the side going IN to the fuel filter and got the same result, no gas flowing anywhere (full tank of gas).
My basic question is as follows: Could the intermittent working of the car be a result of a fuel pump going out and now it just died? If so, how much does this cost? If not, what else could it be?