95 neon problem

[OneddlRyan]

I have a 95 dodge neon with a single overhead cam, and for the last few months I drove my car and it would run good for about 10-15 minutes and then it would be as if it would just want to limp home, or if it was running on on one or two cylinders, kinda like the sound of a lawn mower.
I put in a new cytalitic converter and O2 Sensors, as well as a new fuel pump, and i have a fuel filter that we just havent put on yet, i put the fuel pump on because when we put a tester to check the fuel pressure when it started to buck the fuel pressure would jump anywhere from 0-90 pounds, i think it may be some kind of sensor, im prolly gunna end up bringing it in on mondy to check with the diognositc machine again, any info or help would be awsome.

thanks