I tried the K&N cone on my P5, and it didn't "feel" any different than the K&N Panel and Silencer removed like I am running now. It was actually quieter... for some strange reason.
I was more interested in the amount of air the silencer was letting into the motor than I was the amount of cool air I was bringing in. My horribly non-scientific method of touching the airbox after driving, has shown that the airbox is cooler without the silencer in place. Sort of backwards from what I thought it would be... It seems the Silencer sitting right on top of the radiator, holds a whole lot of heat, or at least gets hotter than the ambient temp in the engine bay... Oh well, it smoothed out the engine enough to notice in the 4,500 RPM range, well, that and the plug wires probably helped some too...