Originally Posted by BadIdea
Do you even need them for autocross? I haven't had a problem even on a big track like beaverun or mid-ohio.
Yep. Don't really think you need them.
The only possible exception would be if you ran a high speed AX like at Cumberland Airport or at an SCCA Solo2 event on a track. Even then, I doubt seriously that you would notice a difference.
The brake duct allowance was put in place for larger heavy cars that employ a closed type of wheel. Mercedes, BMW and the like where heat gets trapped between the wheel and the rotor.
I would say that adding brake ducts to a focus, SVT or otherwise, is unneccessary.