I think I found the answer... straight from GM's Engineering Dept. addressing both Z51 and base models:
Aerodynamics:
Notice: The base Corvette Stingray has a three piece lower front air dam. The Z51 option only uses the two outer pieces and does not use the center section.
With race-proven aerodynamics, every square inch of the 2014 Corvette Stingray exterior is designed for performance and improved high-speed stability. All five air vents are highly functional and contribute to cooling or reduced lift.
All models have a new grille/radiator arrangement and hood vents. Venting air out of the hood reduces total front-end lift for improved steering response at high speeds. The front fender side coves also help vent underhood air pressure to reduce aerodynamic drag.
Models with the automatic transmission or Z51 Performance Package feature a functional vent on driver’s left side directing air over a heat exchanger for the transmission fluid and a similar arrangement on the passenger side that directs air over a heat exchanger for the electronic limited slip differential (ELSD) cooler.
Airflow through the differential and transmission heat exchangers exits through the aircraft-inspired taillamp vents and lower-rear fascia air outlets.
The Z51 Performance Package also includes brake-cooling ducts, a unique rear spoiler and additional air deflectors for enhanced track capability.