The stock fogs create a scoop that funnels air into the IC opening on each side of the car. The area behind the fog lights does NOT go to the intercoolers! It gets directed through the radiator instead. There is a plastic funnel that connects each IC directly to the small bumper opening.
This is the area in question. Lots of area to gather air and force it into the small opening.
If you put in different fogs, this is the area that grabs air for the IC. As you can see it's about 1/3 of the stock setup. Do you want this?