RPM's fluctuate

Well I have the car listed above GS model 5 speed. I will be driving and my cars rpm will fluctuate and make my car jump and nit let me keep going unless I let off and it'll do it again. I assume I have an air leak somewhere but I had just replaced my idle air fuel control valve and it drove perfectly fine all the thirty miles back home. Parked it shut it off went back out to go for a drive and it started acting up again and it smells like burning oil. Have some white smoke coming from the exhaust, there is a healie thread on one of spark plugs a little oil on the top of that coil. Every time my car starts jolting from my Rpm's fluctuate I have to pull over and purge my fuel rail let a little gas out and it'll run normal again for a little while then act up again.
Also engine was replaced has 120,000 on the new engine car has 204,000 miles on it.