general problems of the 2003 Chevrolet Cavalier

On sept 23, 2003 I called the service department at showcase Chevrolet where I bought the Cavalier. Talked to a service advisor about the problem with my vehicle. The car was very hard to handle on groove roads. It felt like the back-end was going one way and the front the other. He said he would look at it, he stated that they put more air in the tires and that should do it. The next day I called and ask to speak to the service manager as the vehicle was worse. Troy (svc. Mgr. ) said he would drive with me. We took the vehicle down the road and it swerved and troy stated to me he felt the problem and was holding on. He told me to take it back as he is not safe in it. He stated that the vehicle was unsafe to drive and that he feels that it is the tie rods. He took the vehicle back to the shop and readjusted the tie rods, rebalanced tires, and stated that he drove the other Cavaliers and all with 14 inch tires had the same problem. I asked him what he could do about this and he stated that the vehicles with 15 inch tires didn't do that and we could buy rims and tires and he feels that should solve the problem. On the third trip to the service dept. He said he couldn't help with the tires as they didn't have any 15 inch rims around and I would have to pay for them. He stated he could not warranty them out as it is an upgrade in the vehicle. I have no way of knowing that putting 15 inch tires on this vehicle will solve the problem. I have contacted gm and they state the vehicle is up to their specifications for that car and they will not do anything to the vehicle or vehicle with 14 inch tires. It was not brought up as an option to me when I bought the vehicle as the gm customer service representative stated. How can they let these cars stay on the road with a problem controlling them on groove roads? the service manager stated that he would not drive this vehicle on the road during rain or snow as you could easily loose controls in the grooves.