I got the idea that the engine died at half throttle both before and after you put on the air filter and took out the needle... from the above message.
I was thinking that although the symptom (engine dying) was the same, the cause of it dying did change.
If you can try reinstalling the needle and then also restricting the air intake i think maybe you might have some luck.
If you already tried this and i'm mistaken about the sequence of events, maybe you could lay them out clearly..
Right now it seems like you corrected for way too much air intake by removing the needle.. (you had too much air coming in so you added some gasoline). A better thing to do seems to be restricting the air intake, not adding fuel to the mix.