I'll put in my 2 cents for what little it's worth.

Many moons ago pretty much all vehicles had a simple air cleaner/filter on top of the carb with a short snorkel still inside the hot engine bay.
Then, on certain High Performance muscle cars OEMs added cold air intakes.
Supposedly, GM claimed that it did add a bit of horsepower.
It quite likely did, probably an immeasurable amount for anyone but them with their sophisticated equipment.

For one, we cannot accurately duplicate a test with and without a CAI. Just driving around and comparing doesn't cut it.

Keep in mind that anything that is done to the air intake changes the HP, think turbos and superchargers to an extreme degree.

Since those early days I mentioned, today there is not any vehicle etc I can think of that does not have and CAI. Even forklifts and other industrial equipment has the extra bucks in their design for a CAI. WHY?
Just something to think about.