I used to have a 93 z28 i bought a set of pullies for it and they caused a vibration in mid rpms this eventually was what i believe to be the cause of timing componant failure. Was the vibration caused from the crank pully not being a balancer, it was just a light pulley probably less than a pound. I took them off the car and still have them and was wondering if i should put them on my 96 but do not want to if that could have been the cause unless i did something wrong?