Some times the idle will stay at 1500-2000 and I can shut the car off and restart and it will go back to 600-700. Also when cruising it feels like I have a miss fire that gets really annoying then goes away and comes back.

 

might be two seperate issues. #1 may be dirty IAC motor. If it sticks it will produce high idle. Key on and off will cycle it and free it temp. I would try cleaning it. Search. I bet all gummed up.

Miss fire? That more difficult. Check EGR function. Search that too.