RPM's running high, loss of power
 

I have a 1989 chevy camaro RS with a 94 block LT1 in it, it had a stock 305 in it before i got it and the guy put the rebuilt 94 lt1 in it and used most of the stuff off the 305 i think. anyways it has always run pretty damn good, but i started having problems with the clutch and then i went into the military and left my car. I sent some money home and got the clutch fixed, but when i came home on leave to drive it, it felt weird and i usally shift gears at about 3000 - 4000 rpm's, now i was shifting at like 7 - 8 thousand rpm's and it felt like my car was not as quick as it used to be??? i have no clue as to why i'm having this problem.