the ebay dp's and tp's are cheap and still offer a performance increase. They are 2.4" ID isntead of greg's 2.5". Plus after that, you can get a catback. If you ever plan to upgrade, you can sell the dp's and tp's if you like (since they didnt cost much in the first place) it isnt so much of a financial loss. Your choice though. Hope you're satisfied with what you choose.