This might help a little. Link to an Aussie tuners online magazine. He REALLY knows his stuff when it comes to modifying turbo cars.
http://www.autospeed.drive.com.au/cm...7/article.html
http://www.autospeed.drive.com.au/cm...3/article.html
http://www.autospeed.drive.com.au/cm...0/article.html
second link is very interesting although the car in question is basically like a vauxhall omega with a 3L sohc skyline engine.