[Luki]

What are these 2 wholes at the front, left and wright of the number plate on the Mines R34? Direct air for the airfilter maybe?

 

[r33 v-spec]

Its to direct more air to the intercooler

They are actually called "Intercooler vents" IIRC.

 

[Luki]

And this is "effective"?
Is it not easier to mount a bigger front with a bigger whole for the intercooler?

 

[r33 v-spec]

Well ay bigger front (i take it you mean bumper) will still not open access to that area.

The area where these vents fit, is right at the top. If I remember correctly, the metal reinforcement plate also has to be cut behind the bumper cover so that they sit far enough, and direct air to the intercooler.

IMO it probably is effective, but again IMHO very slight, and probably not a noticeable gain at all.