Your stock mid-pipe starts out as 2.5" and the stock resonator is 2.5". The mid pipe necks down after the resonator to between 2" and 2.25". If you really want to keep it 2.5" all the way through, save yourself the money and find a local exhaust fabricator that uses mandrel bends, and they can run you a new 2.5" pipe from the back of the resonator to the flange on your Borla. It shouldn't cost you more than 2 hours of labor and a few dollars for materials. Hourly exhaust fabrication labor costs vary too much across the country, but I wouldn't pay a penny more than $100 to have that done.
The stock resonator is damn good.
