AVO makes a turbo kit for the Impreza. It has fit issues with Legacy 2.5i due to a top mount intercooler. Ross and I are working on a new FMIC kit for the '05+ Impreza/Legacy 2.5i. At the end of this month. Full production kits will be avilable late summer this year.
Here is a link to the current turbo kit for Impreza 00-04:
I welcome your input!