The point about "self learning" is loads do it but you have to tell the ecu in the first place, it is just a setting called target AFR, it can be made to hold this AFR no problem.
That however is NOT the problem, the whole point of mapping is each engine will be slightly different even with same components, so some will need a slight more ignition or less fuel etc than others.
Also max power amd max mpg do NOT occur at the same afr.
Closed loop is useful for protecting cats, but if mapped correctly NOT needed.
tabetha