I recently bought a 2002 ls v-6. I've noticed that, at highway speeds, there is some difficulty keeping a straight line without constantly moving the steering wheel slightly back and forth. The car seem to drift from one side of the lane to the other. There is a sort of "dead zone" at top center and a few degrees in either direction in which you can turn the wheel without a response from the tires. I've looked a rack & pinion replacement, am I on the right track? Or is something else causing this problem?