Holy sh*t people. I guess we have all strayed afar and fergotten the purpose of a filter?
I would buy a K&N filter because it filters air better than the stock intake. Sure, air may be able to flow in laminar layers better, but I wouldn't expect much.
Remember, that's the old way of thinking. You can't expect to slap something on and gain a predetermined amount of hp. It's a system. If you want a change in powerband location, torque curve, and peak horsepower, then you have to change the system. The filter is one small, but important, part of the intake system. It's purpose is supposed to filter air efficiently. When you drop in that filter you are not chaning intake tubing diameter, plenum volume, etc. etc.
If you want to add power you have to change the design of the system!