maybe your in fourth gear? lol (ok...being serious now) unless the needle is jumping around....you dont have a problem. did you just put the rims on? the reason i am asking is because maybe you were used to a certain rpm...and then you put the rims on?

clutch slipping would be my guess also...but i think you would have noticed that in the other gears not just fifth. so how is your clutch??? stinky? mooshy? even after you raced the si??? you did say you messed up your 1st to second shift?? maybe you just burtn the clucth a little bit after beating on it?

cel would have nothing to do with the revs compared to a certain speed.