Gentlemen, I have been lurking in the shadows, watching this discussion play out.
1) I have never seen a throttle plate at "Wide-Open Throttle" (WOT) where the throttle plate could actually reach a position parallel to the air flow. Always, they have an angle to them that compresses the air.
2) So long as the plate is angled, it will force air into The Groove.
3) As the air speed increases, so does the compression. Therefore, The Groove will have a positive effect.
You are speaking about a turbo charged engine. What is known as "Turbo Lag" has been reported universally (save this instance) to have been eliminated. Combustion is still enhanced, which gives the conditions necessary for improvements in mileage.
The only factor that can reduce the effects (if properly done and properly installed) is the computer itself. If the ECU has been chipped, or has California Emissions, then it may be locked. If this is the case, you will get minimal improvements (CA Emissions-usually Ford Trucks/SUV's only) but the requirements in CA may be instituted in other nations, of which I have no knowledge and little experience.
One thing is for sure. Every government in the world is running off the money WE provide in the forms of taxes and fees. And ALL governments want to force us to consume more of our resources.
Of course, we want to reverse that!
So, keep up the good work and KEEP THE FAITH!