1997 Saturn SL1 SL1 unsteady RPM

My check engine light is on, my gas milage is horrible 10-15 if it's raining and my rpm randomly goes up and down while driving or just idling even, it kind of bucks like a while horse or bull, and It doesn't like to get up to any sort of highway acceptable speed. I checked for codes several times once it said P0341. I had an oil problem and was not firing in one of the cylindars because plug was fouling but put in hotter plugs and a nonfouler. It had an issue with the coolant temp sensor and the fan was never coming on so changed that and still the fan doesn't come on. I pulled it out and left it unplugged, fan is on all the time which sucks but it runs a bit better. It's revving up and down and all over the place even when just in idle so I changed the tps. Crank shaft sensor was also changed. Cleaned out just about everything I could find. My wires are fine, had an oil change, I dont know what is wrong. I have done everything I can think of hoping maybe it was just a lil of everything but no such luck.