For those interested there is a program called PipeMax. You plug in the specifications of your motor and it will tell your what size header you should have and how long the primary pipes. Then it will tell you what diameter collector you should have and how long.
Also you need to research exhaust termination boxes. They act like and open collector but the outlet is run through the proper size exhaust pipe and muffler. If done correctly you are talking a 30 or so horsepower gain depending on your combination.
I plan on doing this on my 3rd gen.