I'm looking at a photo of my engine bay, and I don't see any nice, convenient, large area for a decent-size hole.
It looks like there's way more room for a hole in the standard location, the passenger side of the engine bay, near the passenger side fender well.
In that photo of yours, it looks like that tube is not very large in diameter (it's sort of flat too), so I'm thinking it may be better to use a larger diameter tube in the standard location, on the passenger side of the engine bay, near the passenger side fender well.
You could even have 2 holes, because there's plenty of room in the standard location.
Unless the air in the cowl is more pressurized than I'm imagining, and I'm no expert on that subject, it seems like it would be better to use larger hole(s) in the standard location, rather than cutting a smallish hole in the firewall.
Also, if you used the cowl, it seems like you'd have a hard time fitting a decent size air filter in the cowl. Unless you use one of those old fashioned disk-shaped filters that sits in the engine bay, over the engine.
Still, it's an interesting idea.