I think I have a problem with the acceleration in my car.  As I get up to 70 mph or so it almost feels like some starts gently pressing the brakes.  Its just barely noticable but I can feel it.  It happens off and on so its hard to track down why its doing that.  The only thing that I know of thats wrong with the car right now is my speedo gear isn't the right size so it says I'm going 10 mph over what I really am but I don't think that is what is causing the current problem.  Any ideas floating around out there that might help please.  Thanks