Is there something special about the muffler for the 912 80hp (that would preclude using another muffler) other than the Rotax muffler has all the attach points pre-welded in place? In my case, my exhaust system has been modified, the result being the Rotax muffler will not work. I have tried other mufflers and have not found any that I have been happy with. I am thinking of talking with a custom muffler shop to get one built but before I do, I want to make certain the custom muffler will meet specs regarding pressures, length, etc, if there are specs like these (or others) that are important to the performance of the 912 engine.