I have a 99 mustang gt. I just replaced the clutch and pressure plate and throwout bearing with a sach clutch kit...when i give the car a good bit of gas, it feels like the clutch is slipping because the rpms go up real fast and then comes back down and doesnt have much power....so what could be going on? any help would be appreciated.

 

Sounds like it's slipping.

Do you have an adjustable quadrant, cable, and firewall adjuster?