ORIGINAL: Phoenixangel
My guess is a fuel delivery problem, its leaning or flooding due to the attitude of the airplane in the air. Try running the airplane on the ground while another helps you lift the plane to vertical it should not really change how it is running if you are getting good fuel flow. If it does change or causes problems I would replace my fuel lines and check tank height in relation to the spray bar in the carb.
Just a gut feeling but it really sounds like a fuel issue.
its fine when I point its nose straight up into the air... it runs fine up until it reaches max revs basically... not really lean on HSN, loads of smoke trails behind until it starts puffing... and the engine head is not hot at all when I land...