I have one of these engines also (what a bear to tune), you also may want to check for air leaks around your needle valve assembly. After countless days of adjusting this so sensitive engine I pulled my lines off of the needle valve (both inlet and outlet) and put a scrap piece of line on one side and held my finger over the other and blew. Guess what ? I could hear an air leak . It wasn't the needle its self but it was leaking around the two orange gaskets. I disassembled it and used high temp RTV to seal the threads, I have no air leaks and the engine is not near as finicky. Just a thought you may want to try, this engine seems to make a lot of power.
Good luck