ok...what difference in hp is there between me buying headers and a cat back set up($600), or just taking my cat hollowing it out,getting a different muffler, and headers ($300) ???i dont really see what the real difference can be..if the aftermarket pipe is 2.5" and the stock pipes are 2.5" why pay so much for stuff that wont make a change?? who cares if the exhaust under my car isnt shiny new...itll get the job done right?