If you're doing it for heat extraction then this isn't the answer. An inducted cowl will do a better job. If you're doing it because you like the look, well... that's a different story.
Where you place these louvers in your hood will determine whether air goes into the engine bay, exits the engine bay, or stays pretty much neutral. Areas near the base of your windshield will generally be high pressure so air will be forced IN. Areas more toward the nose of the car will generally be lower pressure and flow will be OUT of the engine bay.
I'm not sure which would be more beneficial in that respect. I can tell you that cutting air from UNDER the car and creating more negative pressure behind the radiator makes a huge difference on these cars.