You have the high speed needle adjusted too lean. Open it up about 1 turn then start the engine and run it full throttle. When it has had time to warm up turn the needle counterclockwise to richen it till it sounds all blubbery then slowly turn it clockwise till it starts to scream. Now slowly(very slowly ) turn it farther clockwise till it slows down , now you have learned where the needle goes lean. So turn it counterclockwise till it starts to scream again, a little more till the rpms slow down about 200 rpm and that should be your setting.
Now adjust the idle mixture to where it doesnt stumble when the throttle is opened.