Anybody heard of these?

This little gadget could, possibly, maybe affect mpg but it would take a big "IF" working out perfectly.

IF the pump shot atomization is "improved" to the point where the needed acceleration fuel volume and/or duration could be dialed back without any negative results, then overall city MPG could improve.

It's a sad fact that a good % of a carb's pump shot never gets to the cylinder in time to make much difference. This because some fuel is winds up just wetting the intake and ports walls. No biggy for a carb because this "lost" fuel is simply made up for by pumping in EXCESS volume.

A small improvement of city mpg of an MPI system is due to the fact that since its fuel injectors are spraying all its fuel on the back of the intake valve, its acceleration enrichment(pump shot) doesn't "lose" so much fuel to the intake track. This results in better throttle response and mpg.