The air intake in your plane is much larger than the air outlet. It should be the other way around.
Put a round baffle inside the cowl, flush with the lower cowl cutout, leaving only the black section open, (where the engine is).

Hot humid air needs much leaner settings than cool dry air.
At 1/3rd throttle, set your idle needle just lean enough to break into clean non-fourstroking running. Set high needle for best rpm, then back off 100-200 rpm. When throttling up, the engine should accelerate crisply, then slowly climb to best rpm, without sagging.