[elhigh]

Aero mods free up horsepower for acceleration. Fact. Just keep the weight gains under control.

It looks to me like the rounded rear edge of the D-pillar is probably inducing a fair amount of turbulence at flow separation, you could add some small Kammback extensions to those and clean that mess up a bit, maybe add an extension also to the roof edge for the same purpose. If you're competing on track days you'll want to dig into the rules to keep everything kosher with the Tech guys.

For track days I assume you're already pulling all the unnecessary weight out of the car? Passenger seat, rear seat, spare tire? The less mass you have to drag out of the turns, the better.