Remember.. that low speed needle adjustment is very small! When adjusting it, same as the high speed needle, turn it inwards will lean it out, out will make it more rich. Usually turn clockwise for lean, count-clockwise for rich. But, only in very small increments, like perhaps 1/16 of a turn or less.

I played with mine for a good 15 minutes or so, going from idle to full throttle and back, then shutting down, adjusting the low speed mix, then restarting, checking the high speed mix and the transition from low to high.. adjust low.. and so on and so on. After you get it right, though, usually only high speed adjustments are necessary as the day changes (air density, humidity, temperature, and so on).

That's in my limited experience, anyway, others may disagree, but what can I say.