I'm new to this forum so please forgive me if this question as previously been asked. At highway speeds with the cruise set, my 4.7L will suddenly surge up by approx. 200 rpm's. Once it starts it will continue to do it every 10 to 15 seconds until I either shut the engine down or punch it into passing gear. Occasionally it will stop the surging on its own but not often. My guess is the throttle position sensor. Anyone else have this experience? Any suggestions?