'99 Dodge Stratus

I have a 1999, 2.4 dodge stratus with about 140,000 miles on it. Within the year and half that I've had it, I've had to replace the EGR valve, throttle sensor, valve cover, tube seals and cam seals, serpentine belt, coil pack, timing belt, camshaft sensor, fuel filter, water pump, plus the normal tune ups, oil changes and tie rods. Ok. My question is about a week after I had the ignition coil pack replaced the engine light went back on, the car started drivingbad again. On asteadypedal the rpm's would race up and then drive normal after a minute. The engine light goes on and off since then and the car drives fine sometimes and starts doing the same thing on other days. Any help would be appreciated.