[psychorallyfreak]

Are you blowing with the same force as when your mouth was in the big O? In that case, the reason why it feels colder would be because the air is moving faster, and carrying away more saliva from your fingers.
And an intake pipe with a smaller inlet than the rest of the pipe would just be a restriction.
Free cooling for your intake air? Good luck with that, and lemme know the results of your search.