[Mario_Marques]

well, my car does not have one
cfg83, you can do the same thing about the "I use an HAI (hot-air-intake) :" without make your engine breath hot air(hot air is bad for the engine), you can put a resistor in the sensor or, i don't know how people call it in english, a variable resistor control(like the volume controller in the speakers, i think the name is potentiometer), do you get the idea?
We use the same system in performance to cheat the ecu and inject more fuel, you can do the same to inject less fuel.
In my country we call it evry-mod, you can build a manual control inside the car