my muffler seamed to seal up really well when i used permatex exhaust sealer..and i can get it to seal up really well on the extention to muffler,but the extention to engine seams a little tough..i get just a little small leak every time..i have a friend that has a machine shop and i think he has some copper shim in small sheets..i think i will get some from him and cut out a gasket and silicone it and try that..the copper should take the heat and want blow out like the regular exhaust material..make it a little larger on the sides where it want be to flimsy..