Even though 60% more airflow at the same pressure drop across the filter (vaccuum in a car application) isn't important the correlary to that, the pressure drop across the filter at the same flow is. It means a filter with less restriction causes less vaccuum and makes your engine lose less power sucking air past the filter. That is more efficiency and less Pumping losses. That applies across the operating range not just WOT. As pointed out how you get there is important. If it's larger pores, the engine also getting more dirt. I have never seen any results of K&N versus paper filters for particle filtering at their expected flow rate. That would be interesting.

 

Tell me why "restricted" (say OEM paper vs NONE) flow rate is important at any point below, or very near, WOT?

I have the throttle 50% open but only get 45% flow rate. If I can even sense the difference all I have to do to correct the matter is add a little "lead" to my foot.

And, hey, if 60% less resistance to flow resulted in 60% more flow then my 99 C2 would have 450HP.

Efficiency of OEM filter 91% (guess)
K&N 60% improvement = 96.53% efficiency

factory HP 300+/-10% 270-330HP
K&N HP 315+/-10% 268.5-331.5HP