Found this thread (link below) which should stop some of the bantering and answer the question about exhaust design on turbo cars.
Howdy,
This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.
http://www.horsepower411.com/forum/s... threadid=109
Hope this helps.
Steve