My opinion (based on my faulty memory):
If and only if it actually does create an air vortex, then it will create more horsepower. More horsepower does not necessarily mean better gas mileage or worse. But the general trend is more horsepower equals worse gas mileage. Both because of your lead foot (performance) and because of a "virtual" displacement increase. An engine is a pump. It pumps an air and fuel mixture and exhaust byproducts. Pump more air and you pump more fuel which means more power and worse gas mileage. Increasing combustion efficiency is a whole different matter all together. I do not see any way this device can do that. On a carburetor engine though...it could.
The exception to better mpg with power increase being better power to weight ratio effects during acceleration. I don't know how much power this *could* generate versus it's weight, but I seriously doubt it is enough to appreciably affect the much larger power to weight ratio of the MO. Take a turbo charger for example. These add significant amounts of horsepower for their weight. These can drastically increase the HP to weight ratio. But once you have that power, it's hard not to use it. I haven't heard of anyone getting better gas mileage after they add a turbo...just better 1/4 mile times

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Creating a spiraling vortex vice a flat flow *can* make appreciable differences in flow. The problem is, it's really hard to do reliably and across a wide rpm band. Pro shops that have flow benches to test intake mods have been trying to do this for years with some but little success, and not consistently. Although the good shops do get consistent flow increases, they are not necessarily getting it by vortex. As an example, polishing intakes has to be done very carefully and often by trial and error. If you polish too much and in the wrong places you actually lose flow. It's complex aerodynamics IE it's not trivial and I doubt this thing seriously. And from what I have heard, the mods you have to make to attain a vortex are not intuitive and not a simple matter of adding something on the front. And they not only vary from model to model but also across rpm ranges. It requires intricate matching of all the intake components from the filter through the plenum and intake and past the valves right into the cylinder head. All the dimensions including geometry and restrictions are very important. In other words...it may work a little bit at some rpm range but no guarantee across the entire rpm range or on all models of cars. It is more likely that it creates trivial HP increases in some part of the rpm range and lose power in the rest.
But with all that said, it works for you, I am glad for you. Whatever the reason, it was worth it for you. And that is good. You never know until you try, and it is good to try. A test is worth a thousand expert opinions. And it may work for others. So I'm not trying to dis you floaty but I feel compelled to share this albeit faulty memory and opinion to caution others..."Results WILL vary."