No, it is one of those simple science automotive MPG enhancers, that read well but don't work.
It starts with what sounds like reasonable science, "gasoline vapor" will release more energy when burned than "liquid gasoline", but it isn't true in automotive use, it just reads like it should be true, lol.
Carburetors are less efficient than fuel injection for a few reasons.
One is that as the air passes the jets fuel is sucked out and fills the intake with an air/fuel mix, there is alot of surface area in an intake manifold and some of that air/fuel mix sticks to the sides of the intake, so fuel is unused, but no longer in the tank, lol.
(vapor injection would suffer the same fate)
Another is that as long as an engine is pulling in air, fuel is being sucked out of the jets, so when coasting you are burning fuel.
(Same thing with vapor)
Fuel injectors are located next to the intake valves, so most of the air/fuel ends up in the cylinder not coating surfaces, better MPG
Fuel injectors are shut off when coasting, general parameter is when your foot is off the gas pedal(TPS at 1volt), the injectors are shut off until engine RPMs drop to 1,100, then injectors are restarted at idle level, better MPG.
It is better to coast down a hill in gear so RPMs are higher and fuel injectors are off, than coasting in neutral with engine idling
, better MPG
The Feed back system with O2 sensors reading rich/lean condition also aids MPG by doing on the fly adjustment of air/fuel mix.
Fuel injection works much better with the Feed Back system, Feed Back Carbs didn't do as well, but also had the other drawbacks.
The science of energy conversion is not simple but does have some simple rules, the "vapor injection" idea is fine except it won't improve MPG.
Same with hydrogen injection, another one that reads good but can't improve MPG.