My Cel ????

Im going to go later this week to get it check out, but im wondering if you can help narrow it down what it might be. Say When im in 1st gear , and i keep the rpm at around 4,000 rpm, then decide to stomp my foot on the gas, the car feels like it has lost power and the car feels like it slipped( i know it cant be the clutch), And the sound is little different. Well thats the only way i can describe it, i hope you guys can help me out on this. i know this is CRAPPY way to put it

THANKS ALOT