how much top end does this take away and with this kit will it make it able to pull dounts on pavement.

how long do the stock belts usually last on the cluches fells like mine is starting to slip.
when i wedge it in a creek in high gear it used to pull out when i punched it. now it just sits there and like grunts then i put it in low and it will jump right out does this mean the cluch is out?