The 1406 doesn't just have a lean condition. It IS lean. It's the economy version, so it's very lean. The 1405 is the performance version. There are some pretty significant differences, too.
The calibrations make it lean. Whether that's IFR IAB's MAB's or MJ's it makes no difference as that is what sets the flow rates for either air or fuel.
Change the calibrations and change what the carb meters.