The EGO and AFV are corrections which are derived from the measurement of oxygen in the exhaust, using the O2 or Lambda sensor. The corrections are derived and applied to compensate for other uncertainties, such as changes in air pressure, engine to engine variations, air filter clogging, exhaust deterioration, engine deterioration and sensor calibration errors.
The EGO is a correction derived and applied during Closed Loop and Closed Loop Learn control regimes.
The AFV is a correction derived in the Closed Loop Learn (and Open Loop Learn) regime(s) and is applied in the Open Loop and Open Loop WOT control regimes.