TEIN makes decent coils for our cars. Stick to 215 up front and 255 rear. The front will become a little numb when you go bigger. The CR brings 255 in the rear compared to the 245 the standard AP2 has for a reason. Finally get better rubber and the best mod will be get better at your driving, I've seen guys run circles around others with $20k dumped on their cars at the track.

 

+1 on good tires. the suspension is setup great from factory. The car is great at the limit once you figure it out. Bodyroll is not always a bad thing, with a stiffer setup the car may break away quicker and with less warning.