Yep. That was what I was trying to say, and Englishal perhaps too. There is absolutely no reason to fly with the throttle partly closed and the mixture leaned for best power. Because you can achieve the same %power (thrust, RPM) with the throttle opened slightly wider and the mixture pulled back just a bit further, leading to a lower fuel burn (best economy mixture).
The only time you would be leaning for best power is when you want to have (duh) the best power available. That means with a wide open throttle. And that generally limits it to a climb (above 5000'), or the (rare) situation where you want to reach maximum level airspeed, regardless of fuel burn. (Take care not to overrev the engine then though.)
In all other cases you would be leaning for best economy. Or fly full rich of course (if maneuvering, or if the engine is delivering more than 75% power).