Basically what I am saying is that in a computer controlled engine, the computer seeks to run at a programmed mixture based on air temp, barometric pressure, throttle position etc. The part that I think you are overlooking is that fuel is not injected into the engine at one set rate. It is constantly varying in rate a pressure due to the computers program and in essence, if you put more air into your motor, you are creating a lean fuel mixture condition which will cause the engine to run rough and over heat unless it counteracts by inject more fuel to get back to that correct fuel mixture.
Also, as stated, with all the (supposed) fuel saving products on the market. I personally believe the to be in the same realm as the so called miracle diets pills. The pills themselves really do nothing for but because your taking them, your subconsciously tries to be more active and eat better which is actually what's making you loose weights. With fuel saving products, I believe the same is true. Yeah, perhaps some may save you a gallon or two here and there but the cost of investing in them does not offset the savings if any. Think of it this way, (Hypothetically) one or two extra miles per gallon, would save you about 5- 7 cents per tank but if you weight that against a $100 dollar intake. How long would it take you to recoup just what you spent on the intake and remember, until you recouped the $100, you haven't saved 1 penny. Spending money, doesn't save it.