Well guess what i have seen that too. Down here is MS. We have a flying bug that is completely harmless but called a dirt dobber because it builds a dirt nest. i have seen a lot of them build nest in mufflers on motorcycles, 4-wheelers and weed eaters, chainsaws etc.. That always makes a carbuerator run bad. So yea, good idea. Hell take the muffler off and just run your header. Your muffler is not plugged off but it may be restricted. In all my days as a mechanic on that stuff, i have had probably between 75 and 100 plugged exhaust either at the outlet port or the muffler.