ok i have a 2004 scion xa i put the underdive pulley on my car about 6 months ago and ever since i have had to change my ps belt like 4 times it keeps coming off and it broke once and now my car is squelling really bad and i notice the belt is very tore up not sure if i should put my old pulley back on or do i need a ps pump i notice in the mourning its hard for me to turn my wheel i have to let it warm up alittle then i get a smooth wheel im so lost i just bought a new belt not sure where to go next

 

Sounds like the Power Steering is not spinning fast enough and that results in heavier torque loads on the belt driving it . . . less speed more torque.