[Jeff Alton]

I think you mean Castor. Can't be adjusted on a 996 without the purchase of aftermarket arms.

I would start with a trip to your favorite independent shop. Have a tech go for a drive with you to see and agree on the symptoms. My thoughts from reading your post is that your car needs an alignment. One other questions, does it have the same behaviour if you floor the throttle with your hands off the wheel?

Cheers