Nothing.
I'm probably way in the minority here, but the thing that drew me to the BRZ was that it was purposefully built to be an awesome car with it's handling capabilities rivaling cars 2-3x the price, and I don't want to really mess with that. Stock seems to leave a bad taste in peoples mouth, but that only makes sense if you're trying to turn a Civic into a more of a track car; this isn't really a budget commuter car that *needs* to be modded out to be cool.
IMO thinking about performance mods are a bit premature before you even get the car, and really get to know it as it was designed. Which only leaves cosmetic mods, which are really only personal taste. So, the ball's back in your court, OP
