The one I've seen totally removes the vents however. Those vents are there for a purpose, covering them isn't such a good idea.
http://www.motorauthority.com/news/...ght-kit-for-2014-chevrolet-corvette#100417598
Are you talking about that one? That is the one I saw. The little picture says air will pass between teh tail and body. Maybe it rerouted the vent somewhere else?