Good video; NACA headlamp ducts are incredibly controversial in the MX5 Miata world; whether a recessed duct works, whether a raised scoop works better. Revlimiter posted this to demonstrate a recessed duct working:
The debate is all about high and low pressure areas. Many years ago, after studying the debate, I opted for a raised scoop approach, with the original Rover Metro intake (hillclimbing so didn't really care how it looked)
The lid was then passed onto other owners, tweaked, and probably now sits in someone's shed.
I replaced it with a purpose made Dcuatro scoop, about the time I gave upon the Hillclimbing lark.
But DIY is fun.