Here is something weird that has started with my 99 Dakota V6. While driving sometimes the RPM's will increase by 100 for no good reason. I noticed it if the truck goes over a little rise in the road. Also it will do it randomly going down the road with the cruise on. Not a real big deal but very annoying with the cruise on.
Has this happened to anyone else? Maybe a TPS?

 

That was going to be suggestion

 

Vacuum leak probably plenum gasket.