drilling a hole in the back of your scoop?

I would say it makes more sense that any speed increase (track time decrease) seen after drilling holes in the rear or deck under a scoop is simply due to a slight decrease in drag. The holes will allow potential air pressure build up to decrease, which will act to minimize any potential ram air effect. It is a balancing act to reduce drag while increasing performance gains. Certainly if the hood or scoop is deforming or lifting, there is probably more drag being created than I would expect would be offset by any performance increase.

"Dead air" means nothing. It is air under higher than atmospheric pressure, so it doesn't matter if it is stagnant.