I dont know about hood vents but I had side vents (just behind the front tires) on a car back in my car days. The vents were originally just a fake plastic piece but with a little work from a dremel they became real vents. Not sure if they ever made a difference since must factory temp guages are not that accurate but I know after driving a little while and then sitting at idle you could feel the heat coming out of them. I have thought about drilling holes in the side panel on my Metalcloak fenders to give some air flow.