http://www.jscspeed.com/catalog/Subaru/02_07_WRX_STI/Intakes/Short_Ram_Intake_Systems_for_02_07_Subaru_WRX_STI.html
cobb, perrin, AEM...ect.
I had good luck with Perrin on my bugeye, also you never need to worry about buying new filters, just clean it and reinstall