dont be fkn stupid mate,, boobie boy is winding you up, ( am giving credit that the is winding you up rather than trying to rip you off ) ,, how can anybody tell if that is a 57 and not a 54 from the photos you posted !!!! only you can measure it,,, they are worth a lot of money , and as i posted before, they are the exhaust of choice, even for a non R /S .,, if it is 54 ( on a non R / S ) then get a flash to suit ,,, the ball is in your court !!
You must be the only 749 owner who wants to get rid of a Termi system, most would bite their arms off for one. Keep it on and enjoy the noise. You will find an MOT station near you who wont bat an eyelid at a Ducati with a noisy exhaust. It's why they are made.