Maf Map enhancer city vs hwy

[Almaz]

Can anyone explain, why do we need different settings for city and hwy mode for maf/map enhancer? Just by looking at a circuit it shows the pot is in line with a signal so the pot just reduces Ohms proportionally to the signal. Correct me if I'm wrong, is it to compensate more air in hwy mode due to hho comes in after maf/map sensor?

The signal can be easily manipulated just by using microchip/avr and digital potentiometer only if we have a known data that we need to input. Has anyone done that before?

Thanks in advance