My 1998 Z 2.8 with 26K mi on it has started "hunting" ridges on the interstate and has wicked oversteer if you lift your foot in a curve.
The obvious cause would seem to be the new Michelin Pilots that I just had mounted on the rear. These are the exact same in model, size and appearance as the originals on the front, but are in fact 7 years newer and may have different compounds, fibers, or such. Even so I find it hard to believe that the car would change that drastically at normal speeds with any high quality tire.
I am wondering if the yahoos that mounted the tires damaged something or perhaps just the act of lifting the car caused some old bushing to give out. I did get under the car and poke around without finding anything obvious, but did notice that there is some play in the driver-side inner tie rod (the part that attaches to the rack).
If it had happened over time I would suspect the rear subframe bushings or that tie rod, but it happened immediately after getting those tires mounted. Anybody have experience with one of these cars getting "loose"?
PS. I have experimented with adjusting the air pressure, but it did not make a difference.