Originally Posted by 370Ztune

Mainly it's for aesthetics but it also promotes better airflow and cooling. The idea is that the air should flow from the front air dam and travel through the fenders and out of the fender vents. Additionally, you can create small holes inside the engine bay which would relieve some of the heat inside of the engine by by traveling out of the fender vents as well. If you've ever seen the R34 GTR Z-Tune, they also have the same fender vent extensions.