Plugs, wires, and gas/air filter are all good sugestions. I have heard that the intake manifold often leaks between upper and lower halves and around the throttle body. While idling, spray some carb cleaner around these "joints" and see if you get any idle speed "flares".
Also, find an AutoZone store and have them "pull the codes" (around here its's a "no charge") to see if there is anything else wrong.
