Maybe instead of adjusting the high end needle only, try adjusting the low end because the low end seems to "talk" to the high end. You might try to richen up the low end a little and see how it flies because as you stated it does it whenever the nose is pointed up which to me sounds like it is going lean. Also check the fuel system if that doesn't help. Maybe if you haven't already done so replace the fuel lines, filter, clunk, etc.

Well that's all I can think of at the moment.

Extra