In my opinion, there is nothing seriously restrictive about the factory U13 intake.
I have a Finer Filter (Uni filter is the same thing, they bought out Finer filter some years ago....) in my factory airbox and have nothing to complain about. The air is sucked in from just behind the left headlight, so at least it isn't sucking in hot air from your engine bay, which is exactly what the pod filter will be doing!
And by only replacing the factory element with an afternarket one, you are perfectly legal and won't draw attention from the cops if you ever get pulled over and they decide they want to look under your bonnet....
Dan.