stumbling when the motor is started up from cold, but running great and holding a perfect idle after it warms up or when it is started from warm--could this be a symptom of an IAC that isn't functioning properly? It really wants to stumble under load even if I let it run for a good minute before starting off in the morning. Otherwise it runs great. I've done a full tune up with plugs, rotar, wires, cleaned throttle body, adjusted valves.