This might sound dumb, but check your spare tire and jack. Be sure they aren't loose. I know with my new springs and wheels it made the ride stiffer, and i noticed my spare and jack werent' completely tightened. Be sure that you have the spring in its groove on the pearch properly. There should be a notch in the strut that goes against the last edge of the coil on the spring. Be sure those are touching. Be sure its not you tires rubbing, or your strut bumpstop bottoming out..