Problem with the 5 speed is its weak, 350bhp and if you don't drive it with some mechanical sympathy it will shat itself. Can get uprated 5 speeds (PPG, Albins etc) but they are typically 3k + so more than the cost of a 6 speed conversion.
17's will handle and ride better than 18's. Standard caliper is pretty weedy so your best bet is fit a 330mm kit which fit underneath 17's, D2 or similar is a nice cheap upgrade or 330mm 4 or 6 pot Ap's are the daddy. Brembo of an sti are a funny offset so wont fit under alot of wheels. Also braided lines and decent fluid.
Basicly weaps past the seals, so need to pool over time to be visible. not enough to be visible under normal running, but given time to pool you'll see a puff of smoke, my old turbo did exactly that.
I know its been mentioned before, but finaly getting round to playing it online.
Is anyone still playing it? or point me in the direction of a decent active crew?
http://cobrasport.com/index.php/cobra-sport-exhaust/subaru/impreza/subaru-impreza-sti-turbo-hatchback.html
also stay away from anything with a mesh section in it