One of the biggest misunderstanding in the performance engine world is Ram Air. The average supercharger works pretty hard to generate just 3 to 8 pounds of boost. A ram air hood isn't producing measurable boost until 70+ mph but we aren't talking even 3lbs. Below that mark the biggest benefit is to cool the air charge.

During the 4 stroke process there is a brief time when both the exhaust and intake valves are open. At low boost like a scoop would supply most of the added pressure (if any is produced at all) would simply be wasted out the exhaust port during this overlap. The exhaust valve does eventually close while the intake is still open but not long enough to let a meaningful amount of additional cylinder filling. So the "functional" scoops help by dropping the under-hood temps which helps right where the most heat is being created, the exhaust manifolds. Forcing that hot air downwards under the car keeps the cool air coming in the front grill that much cooler. It also drops the temp of the intake manifold and runners.