I've been reading this board for about 2 years(just joined last nite) and by far the most numerous suggestion for Ex. Dia. is 2 1/2 ". On a stock 240 this has 237% the volume of the stock system; the factory gets 150hp (gross) from this system with a restrictive muffler.....if we multiply that by 237% we get 355hp and maybe more with a less restrictive muffler which most owners do. I would bet not everybody gets those numbers.So my question is ; is that large a diameter needed especially when most of the hp figures that I have seen posted on this and other boards is in the 200-250 range( we are talking non turbo applications here) Using this logic ( it's probbaly flawed) a 2" system would be in the 275hp range. Am I way off base here or not?