[Christ]

Yeah, he's claiming that by increasing turbulence aft of the throttle plate, you're creating a resonance that is, in effect, a supercharger at certain speeds. Of course, intake length/cross section tuning achieves this as well.

I'm not entirely sure that those grooves will do anything except completely kill the flow velocity, but I can assure that at higher throttle angles than cruise, they won't be increasing horsepower, as they'll be restricting airflow by creating more turbulence. Keep in mind, even pipes have a boundary layer. The effective cross section of an intake pipe is actually smaller than the visible cross section, and is increasingly so as intake velocity increases.

There is no evidence that a completely smooth intake tract is any more beneficial than a lightly roughed up one, but I'd be extremely wary of grinding out any kind of slot in my throttle body and expecting any gains from it. They're usually not cheap to be carelessly modifying.