I had Koni Sports (from Sam Strano - good deal, quick shipping - fact) with FRPP "P" springs on the '09 GT/CS. On the softest setting the performance was much improved over stock with only a little ride change. Dialing them up made autocross transitions much more predictable and controllable. For a serious competitor the difference in tuneabilitiy for street versus track was very much worth it. As I understand it, they are single adjustable, changing only the rebound action.

I don't have any experience with STR.Ts.

 

Thanks for all the insight/advice guys. I'll post pics when I complete the install.