Tests with the "high flow" air filters have shown that the airflow through them may actually be worse than a paper filter, in addition to inferior filtering properties. Why?
While the media itself flows better per square inch, the pleats are much shallower and therefore there's less surface area.
In any case, from personal experience, the simple drop in filters don't yield a noticable change in performance (for better or worse). I've used cold air systems before and they do sound cool but no measurable increase in performance. After years of a cold air intake on my 2000 Sport, I reinstalled the stock airbox.