Can I turbocharge my Impreza?
Yes, there are a few different ways to go about doing this. 1st is to simply swap in a motor from a factory turbo Subaru. 2nd, there are a good deal of turbo kits available for the Impreza.
www.forcedairtech.com is one of the companies that makes them, there are a good deal of other companies you can find by searching around. 3rd is you could build a custom kit. This is the most difficult and complicated way, but can also be one of the cheapest, and you get to use exactly which parts you want. This is the route I'm taking