Also check your PCV Valve and hose...mine had similar symptoms and when I changed that it settled down...just a thought.

Sometimes too when I disconnect my battery for an extended period the engine will seems like it is slightly "revving" between 500 and 1500 rpm...after awhile it settles down to normal though...

White smoke typically means antifreeze...(blue=oil, black=fuel)

Hope I've helped and not confused you further...

Jason