striaght w/o cat or resonator....

2.5 inches... seems cool though... not rreally restricted....

 

Just purchase a HKS Hi flow and run a custom exhaust. I am not sure about where you live but in MIA we have a good muffler shop that does mandrel bent pipes any size you want. And by the way a turbo does not need any back pressure like NA cars so the more flow the better.