i had the same exact issue happend to me when i went from my stock rims to my 19", i went back no lie 6 times to get my wheels balance eventually the problem got better, remember the lexus is a very picky car what i was told time and time again is to let the tires mold to the road it will go away but it will never ride the same as with the stock wheels, also make sure your getting a high speed balancing done on ur tires