I tried it. No joy.
In retrospect I realise that it could not have possibly worked for mileage. The throttle restricts the air flow anyway so increasing it by ram air would just be compensated by restricting the flow using the throttle. zero net gain and cooler input temps.
The only case where it would make a difference is at high speeds with the throttle wide open. I could not detect a difference, but we are talking only a fraction of one PSI difference.
Too bad. It looked cool. :wink: