Us some blue loctite on the screws to keep the muffler together. As others have said your low speed needle sounds off. You actually run on the low needle untill around 3/3rds throttle. The low needle adjustment is critical. I also agree, ditch the 10-6, too small. Start with an 11-6 and go from there. Good luck with it. A Fox or an OS plug should help. I have read where these engines sometimes have a taste for an idle bar plug. Try one and see how it works. I have used Fox's for years and always had good service from them.

Mark Shuman