Re: pulled studs,loose studs.
At our altitudes we encounter a rich condition due to the thinner air. I doubt that you're starving for fuel. Your problem is not enough air. Move the 'C' clip on the carb needle up to the top notch and drill some holes in the plastic air cleaner housing. Keep your holes in front of, or before the foam element. I experienced a little performance gain by doing those two things but then I'm about a thousand feet lower than you (6400 MSL) Some guys have reduced the size of the main jet by soldering it closed and redrilling to a smaller sized orifice. I've never felt the need to do this because after break-in, my engine began to perform like I had expected and keeps getting better with age.
Your spark plug is a good indicator of running condition. If you're using the stock, (kit supplied) spark plug, replace it with a better quailty such as the NKG 5 or better yet the 6 plug. The six is a little gotter plug and seems to work well at higher altitudes. Keep us informed on your progress.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"