This “tube” (not sure what you want to call it) connects the cold air hose (also connected to air cleaner) to a “cap fitting” (again, not sure one would call it) that sits just behind the front bumper. There is a black barrier panel to prevent “sprayed up” water from entering this entrance just above and below that entry cap fitting.
The fitting itself is molded from black plastic (as well) and has a a flat panel on front most edge that somewhat closes off the cap. I tried to get photos of this on both of my cars but it wasn't visible.
This is a picture from the parts manual:
I'm not sure how restrictive the "blocker plate" is but for stock (non-modified) cars, it is not a problem. For performance cars - I can see altering that plate for less restrictive air flow.
BudW