Since we're on the subject of turbos, does anybody know if there's an aftermarket VNT turbo available for the Impreza? If you don't know what a VNT is, check this link:
http://www.xmission.com/~dempsey/shelby/sheldod9.htm . The car you see at the link is the CSX-VNT it is a Shelby Dodge that came stock with a VNT turbocharger. The whole concept and function of a VNT turbo is explained at the site.