Front end problem

[robjr69]

I had my tires(on the stock wheels) balanced the other day and it still bounced between 60-70 so I took it back and was rebalanced. it still did not help and I told the guy he sold me the pirelli tires over 4 years ago and I only put them on in the winter. He said since i havent drove on them long enough they probably got hard and dont perform like they should. So he warrantied them out and I bought some yokohama tires and now my car drives worse. I cannot go over 55 without it bouncing really bad and the steering shakes. I have had a intermmintent popping sound in the right front that the dealer could not locate cause it wont do it when its there. it has gotten worse the past few days. I went back to Discount and the guy rode with me and said that its not a tire problem I have something wrong with the suspension, maybe a strut or mount, and that he could feel it shaking and moving back and forth on the passenger side. WHat could cause this only at high speed? We thought it might be the tire so to rule that out we swapped the tires around and still the same thing. I also can feel something rough through the steering column on bumpy roads. dont feel as solid as it used to. I do know that I had got the history on this car and the service guy at the dealer said it has had the steering box replaced twice in the car since it was new. I guess that is the rack? If someone has had the same problem can you please advise.