It allows you to flow as much air as possible. I have a grand total of 200 mm of throttle body on my manifold. Makes a great deal of difference when upgrading from what... 60? 62? Keep in mind as well that unlike an enormous single throttle body, intake air velocity isn't dropped as much, since you just have a straight runner down to the intake port.

In addition, each cylinder recieves an equal portion of the airflow... there's no intake manifold that may for example bias cylinder three (in the case of many Hondas) or the like. I can tune each throttle plate individually to gain any results I want, in addition to modifying all the plates at once.

There's still a fuel rail with injectors. I can take some move pictures for you if you would like, but that's the fuel rail right below my knee.

I'm doing it first because I'd rather not waste my money on injectors, rail, FPR, skunk2 manifold, and an oversized TB when I can get all of those in a package deal with MUCH better results for not too much more money.