Originally Posted by feta_mgp
Just did a google search and every image of the ST I found that was a production model, like our model had an opening at the top of the grill for the intake, and an opening near the bottom, not very big, like ours, for the intercooler/radiator. But even though it's height is similar... the grill on the ST is wider than our center portion, so it will be a bit bigger. As I stated, easiest way to do it with a standard bumper would be to take a dremel to the side grill pieces and make them functional.
That said, there IS a larger opening at the very bottom of the grill, where they have a much wider air dam than the traditional Focus' small 4 holes.
Yes, the lower opening above the under tray but on top of the air dam is slightly more open, now how much of an effect on the cooling this is, I'm not entirely sure.
However I'm sure that if you had really wanted to put the standard bumper cover and grille panels on the car instead of the ST specific pieces you will have to either open the triangular grilles or dremel holes in the lower air dam to mimic the ST.
The remainder of the air induction portions of the grilles are the same just styled to look differently.
The main bulk of the air currently is coming in through the lower grille, between the area blocked occasionally by the shutter system and the lower openings in the front bumper cover/ air dam.