I will try to give you the short version to your questions. There are basically 2 types of pulleys: Crank and supercharger(SC). For the SC, you have the Code 3. For crank pulleys, you have 178MM, 181MM, and 185MM. The SC pulley is the easiest to install, and is comparable to the 178 crank pulley. The purpose of these are to make the SC spin faster, creating more boost, thus more power. They do a very good job of this. The pulleys are on the front of the engine....located within the series of pulleys that the serpentine belt goes around.

Wheel spacers.... They change the offset of the wheels. Many people use them to get the wheels pushed further out from the axle. This allows the tires to line up more evenly with the outer fender well vs inset inside the fender wells. This gives the car a much better looking stance.

I hope this makes sense, and clears things up a bit for you. If you have additional questions or need clarification, just let me know.

EDIT: I agree with 240M3SRT... Code 3, NW CAI, and a Eurocharged Dyno Tune. Then hang on!!! Oh, and get some sticky tires so you have some chance of controlling tire spin.