althepal88 I am disappointed to hear that the DLE 20 is a no go . That is what I was planning on using . I am still waiting as my plane is still on back order . I noticed in the pictures of the Cub with the Evo 15 installed that the muffler that was being used was sort of a square looking unit that fit under the motor mount . Not the same muffler that is displayed in the Evo 15's display spec page . I was wondering if you knew if you could use the stock muffler or would you need to purchase a special muffler? How bad do you need to butcher the cowal ? I already have a DLE 20 . If I had known that I was going to need to purchase an Evo. special for this plane I might have rethought ordering one . My buddy just bought one and the first one failed so was replaced and the second one he was unable to keep the muffler tight on it so he lost the muffler . The muffler cost I think it was $90.00 . So I am at this point a wee bit shy of Evo. engines . His second engine does run smooth as silk an has lot of power . Its the Evo. 33 . Anyway I would really like to know if I do get an Evolution 15 GX am I going to still need a muffler ?