Restricting the airflow can save gas. My own very first car, a 1961 Rambler American, got 30 MPG at first. It would only go 60 MPH on a level road, slower uphill, and faster downhill. Then I found that the throttle linkage was only opening the throttle partway. Fixed that, and got 24 MPG after. But then I was driving 70 MPH.
So there. Indisputable truth that intake restriction improves MPG.