I find no problems with my 2005 roadster with the stock Contis (6700 miles). I did have a tire with an invisible screw letting air escape slowly, but once that tire was replaced everything functions just fine. My XFire tracks well, changes lanes with a touch of the steering wheel, and stays straight in braking situations. Perhaps the roads you travel on a regular basis are worn by heavy traffic and you keep getting caught in the groove giving you the "squirrely" feeling. Are there any roadways that have been recently repaved that you can try your car on to see if there is any difference?

Bob