2003 Volkswagen Jetta Car Troubles

I have a 2003 VW Jetta. Lately the engine has been stuttering and the revs have been going up and down when the car is in reverse, or if it has just gone into drive from reverse. The stuttering, though not prolonged it is intense and it feels like the car might die(it hasn't yet). Also after driving at either high rpms(highway) or just accelerating quickly, the car makes an odor that is very noticeable. It smells kind of like burning plastic or a rubber of some sort. Is that connected to the stuttering problem? How can I fix my car?