I'm willing to bet that Gruppe M didn't do any wind tunnel testing. Do you know how much it costs to use a wind tunnel? I don't, but I know that you have to have A LOT of extra cash laying around to get anybody who owns a wind tunnel, to let you use theirs. Plus Gruppe M isn't that big of a company.
I've also read sowhere else (mind you, this was on the internet, so I'm not taking it anywhere near 100% accurate), that the Gruppe M takes most of it's air through the side opening in the engine bay, and that the cowl port isn't that big at all.<<That I can absolutely believe.
Gruppe M's intake for the Euro Type R is completely different than the one for the FD2. I'm still undecided on the Euro intake. It can be seen in the thread posted below:
FN2 GruppeM - Civinfo
I actually prefer the airbox for the Euro R, because it looks a lot more functional than the FD2 airbox. It's just the method Gruppe M uses to scoop the air for the Euro box, that I'm not 100% sold on.