Gilly, sometimes it would change the idle and sometimes it just stays at 6-700. I also feel like something is pulling me back while I'm driving (rpm between 2500 - 3000). Also, the car sometimes shuts down as I approach a stop.
I changed the plugs because of this symtom hoping to solve the problem. Today, I opened the door locks and opened the right rear passenger door. I heard a hissing sound coming from the door mechanism and I heard the vacuum pumping longer than usual. Could this be one of the causes of my problem?