Unless you are planning on doing a water/alcohol injection then you don't want any smaller than the 3.4" pulley, as said before. I have this pulley and run 93-94 octane and still get detonatioin at times. I know i need to cool the charge dowm more even with my 3.4". Just change those to start with and see what you think it drives like now.
Oh...and the intercooler is a water to air heat exchanger that they machine the top of your intake manifold and sandwich betwen the blower and manifold. It is great for cooling the ari charge,,,,,but you won't need this unless you get really serious into the mods. And this costs around the $2500 range once you have all the necessary equipment.