I own a non-turbocharged car, and dont know much about turbo modifications. Check the links section if you want to learn more.
I do know that if you want to upgrade your turbo make sure to upgrade the intake, intercooler, uppipe, and downpipe as well. Also, remember what I said in the engine section about certian parts only being able to take certian amounts of power.
This is an example of a big turbo.
Specials
**New**
STi intercooler, new in box only $215.95. Great price for this usually expencive OEM part.