On most efi hat setups I've seen they block off the two outer butterflies so the center is the only one that flows air. This makes it much easier to tune and much more predictable. Really helps you take advantage of electronic fuel injection and the benefits it offers over carbs and mechanical such as mid range, fuel efficiency, cruise, idle...things like that.
There is one small issue with that type of setup. Airflow thru the butterflies is anything but linear. Its down right terrible. Like AP said, they usually block the two outer butterflies to help, but its a band aid at best.
EFI is 100% dependent on perdictable air flow or a least a mass air measureing device. Trying to map a speed density or Alpha-N system with a hat is not a amatuer undertaking.
This boat is working out a EFI and hat deal. Its not easy and they have one of the best in the business working on the system. It has custom built butterflies that help make the airflow much more linear. They aren't blades like a normal hat. They are more like the center cross section of a ball. The blades are thick and the sides are curved.
Its not working all that great right now. They will get it, and it will work. But its not a simple thing to work thru. Specially if you think a MFI is tuff. MFI is a walk in the park compared to working thru a deal like this.
You thinking of that on a t ram base, or a blower?
Part of the issue with the pictured setup, is not having enough injector. The current setup I am working on is a hat like this but only has 4 injectors and even with 4 - 160s it is not enough. So make sure you have at least enough fuel for your combo. I would even make the injectors larger than you think you need for a blown setup. I have tuned many of these with EFI and they are not a walk in the park but can work just fine if you know what you are doing. Alpha N has no place in tuning something like this.
From what I found dyno testing most engines become more driveable by blocking at least one butterfly. Most of the engines lost a little power by blocking the second butterfly.
I have also used Robs "Rootz EFI" plate and it not only looks nice but works well too.