joshie... I just ordered a new cen pipe after a bad crash... don't ask.... its about the same as the one you have... I run an os 18 now.. the exhaust size is the same as the cen comming off the engine.. just dremel the sides a bit to allow better flow... I do that with my cen pipes to allow better breathing.....the cen pipe as well as the kyosho uses pretty soft aluminum so its not hard to do..