Blue, i think you are a bit mixed up. The device wont replace any air that would normally come in through the throttle body. But instead add a little swirl of air into the mainfold which they say aid mixture of fuel/air. However, i really dont think it can do this effectively since it works on the manifold vacuum, which oly really appeard on overun. So, wont affect on throttle fueling. It works in the same way an old device for carbs worked, When the engine in in overrun, there is a vaacuum in the manifold, this would normally mean that the acrb would be trying to supply air and fuel eventhought he butterfly is closed....so the unit would put small amount of air into the manifold, meaning teh carb would supply less air, thus less fuel, aiding fuel economy. But this ecotek device has so many false claims and flaws it really doesnt work as well as it should. For example, where the unit is placed (nearer cylinder 4 for example) how the swirl would be erdicated by tumble as air flows over the valve......etc.etc