I have flown my 2300 about 4 flights and each time it went lean with the nose up at less than full throttle. It never quit, just slowed way down. I replumbed the tank with large tubing and ran the engine on the ground. What I learned is that the low speed needle controls the midrange mixture moreso than the idle mixture. Before, at the flying field, I would hold the nose up at full throttle to set the high needle, and set the low needle by the idle speed and transition. This setting proved to be very lean, as the engine would go lean quite often, even during a slow roll. What I did tonight was run the engine up to about 3-4000 rpm and hold the nose up. It would lean out and slow down. With the engine still turning 4k, and the model on the ground, I adjusted the low speed needle open, till it sounded fatter, and raised the nose again. This time, it started that lean rattle, but basically held rpm. A few more tries at adjusting the low needle paid off, as now it holds power and doesn't rattle at low throttle settings with the nose up. Idle rpm came down, so now the barrel needs to be opened up to get the same rpm. Transition is perfect, and as an added bonus, the throttle cut actually kills the engine now. Used to be that I would have to stop it with my foot. I have yet to fly after making these adjustments, but I'm sure I have done a world of good for the settings. The engine is swinging a master airscrew classic prop, 18-8, at 7700 peak, which I think is good at this point. Pulls my F90 way easier than my OS 1.08 did. I think I'm going to like this engine!!