Interesting. I'm waiting for my custom painted gills from JleviSW (orderd Satin Black) and when they arrive I'm going to swop them out. I never realy looked far into the gill but I thought it was a vent.
I wonder if removing it would cause noise at speed or crap and debrie to start dirtying up the side of the car. Post what you find. I guess you can allways put it back on if there are problems.