You really want to keep the under hood area isloated from the passenger cabin. If you remove this strip you allow heat and whatever fumes to easily enter the cabin.
Should you have an exhaust leak I don't want to be in your car. Even the extra heat being drawn in during the summer isn't a great idea.

 

Good point obe.

I've already Swiss-cheesed the back of my airbox some time ago which of course also exposes engine bay air to the cowl area (I have no box or filter there with an HAI, so it's wide open). From the cowl to inside cabin, I recall a large hole with rubber grommet near the steering column, but that's about it. I would think any hot air entering the cowl will want to rise, and also when the car is in motion, drawn-out even more so through the cowl vents...