Best bang for your buck is to get the cai, 65mm supercharger pulley, and a tune from eurocharged. Later on, you could get needswings intake manifolds for another chunk of change. Now if you have the money and want to put more work into the car you can get a 62mm supercharger pulley or the 185mm crank pulley, but with both you are going to need fuel(pump, lines, injectors), cooling(isolation kit, supercooler), and traction(wider tires, limited slip differential) upgrades. Headers and exhaust don't do much on these cars. Just remember that the more you do to the car, the less reliable it will be. Decide whether you want a reliable, street car or a fully built, less reliable track car and go that route. Also, I'd recommend an oil catch can for general intake/engine health because the stock pcv system sucks. If you get a smaller sc pulley get a pulley saver/belt wrap kit and you could get a scatter shield to help minimize the damage should your aftermarket pulley decide to break.