Perhaps you should add ballast to the car so that it hyrdoplanes less. Maybe 400 .lbs or more so you can reach the 4000 .lbs mark. RC mentioned something along these lines would help it go around the Leipzig test track faster than a CGT! Oh, and you might need to have some springs with a higher rate made for this purpose.

Seriously though, your situation sounds about normal to me. Tweaking the tire pressures a bit could very well help so play around with them.