Do you think there is a possibility there isn't a thread on this by saying 'sorry if there is a thread on this already'? It seems like you found this forum, registered, and immediately made this thread. Right below the model specific section is the technical section with threads dedicated to turbo powertrains. Right at the top is a sticky, and this thread right here......http://legacygt.com/forums/showthrea...st-178684.html
The thread you made up there looking for quick help is never going to work. You're going to get 30 responses with at least 15 different ideas. Everyone has their own opinion. Taking a couple days to read allows you to make up your mind because you know your situation and exactly what to do. At the very least, researching will get you informed, and then you may ask questions to help narrow you down to something, or to learn about a particular setup. General questions like you asked end up going all over the place.
This thread is lengthy, at times it goes off topic, but it is a great read. I recently went through it and it's great info. http://legacygt.com/forums/showthrea...de-119177.html