Thanks Ken, for answering my question about CO2 for welding with a MIG. If you want something to test your patience, try the aluminum welding rods used with a Propane Torch. When you think about it, there is a lot of skills involving technical knowledge that modelers learn to do. I have been in this hobby for many years and have been amazed at what others can do more than once. It all makes for very interesting people, modelers in their particular hobby, and radio control for example has evolved into a technological industry of it's own. I saw and used the very early radios and they were Dinosauers compared to what we have now. I don't really have the desire or the patience for Museum Scale RC models, because no matter what I will fly them, but I have seen models that look as good as the full scale versions, at least. A TIG system is pretty expensive for welding a few mufflers, so I would "test my patience" trying it with a MIG. I once worked in a fabrication plant, they welded all metals. They called one system a "squirt gun welder", I guess it was MIG and they use to roll 1" thick aluminum plate into large diameter pipe, bevel the edges, and then fill the "V" on both sides with Aluminum welds. They also used one of those "Railroad" systems to hold the gun and crawl across the seams. I remember seeing some beautiful welds. Yes, I know this was very heavy metal, much heavier that .060" model engine mufflers. I learned something else lately, the older you get, the more stories you have.