Anyone ever try it to extend the life of a muffler. Products such as Corroseal converts rust to an inert substance so I would expect it should be okay. As I am installing my freshly rebuilt K321 I am cleaning things up. My 1989 muffler is still good, but certainly crusty on the outside. I was thinking I could pour some inside and shake it around as well. It may help extend life. Anyone know if these products are not appropriate for high heat items?