I would not play with the low end at this time. Open up your Thunder Tiger muffler and remove the baffle. It works like a restrictor. You don't need it. Replace your Tower muffler with your stock Thunder Tiger. I run Omega (pink) 15% fuel. You can use 10%. I broke my engine in at 2 1/2 turns and it runs great now at 1 1/2 turns. I have never needed to adjust the air mixture screw on any of my Thunder Tigers.

Good luck!