I think it is a gimmick at worst but possibly better in certain scenarios at best.
If feathering out the accelerator pump shot does actually help, then it would only be scenarios where there is a constant fluctuation of throttle is in play, perhaps on a road course, maybe heavy city driving.
It looks like it may obstruct airflow through the carb, which would affect top end and WOT scenarios negatively and may affect lower rpm performance.
I looked for reviews but found nothing with substance. They all amount to I installed this, the engine runs, performance is good. That tells us nothing without a comparison. How did it run before and how has the addition of this item affected that? Ideally, this comparison needs to be done by someone with a more scientifically minded approach and who actually knows how to tune things but some sort of comparison is better than none at all.
One thing that is certain, you cannot trust what a manufacturer says about their own product.
If you have the money, try it but it is a lot of money to spend for potentially no benefit.
Lawrenceville, GA