In my opinion, once the aerodynamic correct balance (either full stock TT bodywork with a small lip upfront, or full GT2 factory bodywork etc..) the most important aspect to fix is the toe-out settings of the car and camber.

If you want a high speed car (lot of highway miles) rather than sharp turning, reduce the camber front and rear, and have a neutral toe setup, to a slight Toe-in even..

If you have worn out bushings, you will not be able to hold the correct toe settings once the car is subjected to downforce or lift at high speeds, they will change with load changes, in a quite large way, and kill stability.

 

Another apparent weak spot is the inner steering arms; the rubber softens with time and allows toe changes. It would appear only the GT2 has solid arms, all others, including the RS, have this rubber inner.