i've ran almost 9 tanks thru the Magnum XLS 46 (breaking in). I adjusted the High Needl first and not much with the Low needle. I get a smooth transition from idle to Full Power. I can point the prop straight up with full power with a noticeable increase in RPM. I can point it straight and back up and the engine still runs.

I then decided to simulate what would happen in the air. At full power I I pointed the prop straight up and then cut the fuel to quarter stick. engine running fine. i then pointed it down 45 degrees less than quarter stick and then increased throttle at horizontal. the engine stuttered and then died. I repeated this a couple times and noticed it happens only when I point the prop down and then straight again.

Could it be the clunk not reaching the front of the fuel tank while nose down? If so, what do I do? or this doesn't happen in flight?