I have been experiencing some fluctuations in my RPMs while cruising at a constant speed on the highway. In cruise control and not in cruise, the RPMs will jump around 200 while I am going 50-75 mph. Every time I hit a bump in the road, they surge like I am pushing the gas pedal. The truck doesn't accelerate, it just revs the engine. The RPMs do not surge will idling. Not sure what the issue may be. I cleaned the throttle body a few months ago and there is no check engine light on. Any suggestions on what the problem may be?