I'm having some difficulty in removing the carbon from my muffler. I used heat to burn out most of it, but I found that there were some chunks of carbon that I couldn't shake out of the standard exhaust, which reduced its performance. I do not have access to welding tools, so are there any chemical or physical ways to break down the remaining carbon? I've heard of caustic soda being used, along with brake fluid, gasoline, or oven cleaner. Any advice?