2. Read the first 2 pages of every post in every forum before asking any questions, I promise that it'll be time well spent.
3. People on NASIOC can be kinda' mean, just keep that in mind.
4. NASIOC is worse than a High-School Clique.
5. Forget about BOV's and Boost Controllers.
Here are the most popular mods for the STi...
Lowering Springs: Tanabe GF210's
Down-pipe: Helix (catted or catless) bellmouth
Engine Management: Cobb Tuning AccessPort
Intake: K&N Typhoon
Sway bars: Cobb Tuning
No, you can't use the OEM Bridgestone RE070's in snow, get some Pirelli PZero Nero M+S's if you don't get a lot of snow, and some Blizzaks if you do.
Make sure to get to know your car before you mod it, the car is plenty fast from the factory, and please be safe
Oh yeah, almost forgot, don't bother chasing down squeaks and rattles, the moment you cure one 5 more will pop up in its place