I recently purchased a Hayame flange & b.o.v. kit from www.spwusa.com.
The kit replaces the factory blow off valve. The Hayame flange is a CNC machined billet peice that allows you to fit the Blitz b.o.v. It is supposed to reduce the lag a bit and protects the turbo from pressure surge. The kit came with all hardware and I installed it very easily. Now everyone notices it as soon as i open my hood, plus everyone gets to hear that tight sound when i drive past them. I love the kit and reccomend it to any WRX owner. Check out thier website they seem to have a lot of JDM lighting and accessories, like the JDM WRX headlights. I cannot afford those yet but they do look nice.