Let me clarify by saying I'm not a dumb buyer and when I picked this car up for 2500$. I thought it was a steal. No check engine light idled perfectly at 750. now after 200 miles. It sounds like someone put in the largest cam profile allowable idling 600. Are idle misfires common? I looked at the computer and the adaptations haven't changed so I don't think there's a vacuum leak. Any possible answers?