I went through the same thing as you, all of the same mods same problem but when I switched to a 168 main ,48 pilot, red needle at the 4th position, and Zip-Ty 1.5- 2 turns out depending on temp and altitude. The bike runs fantastic and no more stumble. James Dean gave me these settings because I was having such a hard time with my jetting I think the blue needle is just too rich for some bikes. Good luck... Sounds like I have some experimenting to do, I never considered going to the red needle just because it's so cool here right now. Were averaging 45 degrees right now.