"Ask any dyno operator/tuner."
You called
(although most of my work has been with carb'd cars)
Most ECUs don't know what gear is being used so thats a non-issue.
The map does not normally determine the possible tuning range of the closed loop system. Thats usually determined by the control program. Without these limits it could really screw things up. The map is really just the starting point.
But you are missing a couple of rather important factors.
1) If an engine was running too lean it would fail emissions.
2) everything you've mentioned really only applied to steady state running, ie fixed RPM. The moment you alter the throttle settings the ECU goes open loop. Emissions are measured at a fixed RPM plus lambda sensors are too slow to react to the quickly changing RPM. You HAVE to add more fuel on acceleration otherwise the engine stutters, this is what the accelerator pump does on a carb.
(most ECUs sample the lambda reading once every 0.5 to 1 second)
3) ignition timing
Power is determined by more than just fuel. The timing self adjustment on most ECUs is either nonexistant or VERY limited and is usually set for hot air and cheap fuel.
Tuning is a combination of fuel AND ignition. Hence the market for chips, piggyback ECUs etc.. If it was just down to fueling it would be an easy job.
