I do not exactly how to describe this I am going to try my best. Ok I have the 350 TPI and when I am going down the road my car stays between 1500 and 2000 RPMs which is right but once i let off the gas it drops to 700-1000 RPMs although I am going 55 or 60. It like 2 to 5 seconds then with out having to push the pedal down the RPM goes back up to like 1300 on its own any ideas what could be causing it to drop like that?