I could say use the search button that would be too easy....... Changing a rear muffler on a Sportivo is a risky thing to do. most of the fart cannons etc you buy are simply straight through and have NO BACK PRESSURE. Sportivo corolla's are very sensitive to back pressure. too much you loose power and too little you loose power. CES have done the homework and tried several rear muffler combo's to find which one worked the best and yielded the KW increase combined with the rest of the system. If you want a specific dyno comparison between stock and a cannon and something else then you may have to do it yourself. I have done my part in the development phase of stuff for the sportivo and cost me plenty of time and dollars. so if you would like to step up to the plate and continue then be my guest. Can't wait to see the results. Sometimes you have to do stuff for yourself. You cannot always expect somebody else to do all the hard work for your benefit.