More air into the engine will equal more power. Plug your filter and see how much power you loose. To determine if a standard pleated air filter is restrictive, air pressure would have to be measured after the filter. Ideally, there will be no measurable drop between atmospheric and post filter measurement. If there is no measurable drop under full load, there would be no benefit to a K+N. If there is a drop, you are loosing power. How much is anyones guess. Run you engine without an air filter (testing purposes only). This is as much air flow as any filter could ever deliver.

I originally asked the question because I do have a life and really can't justify spending the time to measure my air filter restriction. If I searched instead, think of all the bickering we would have missed! Hey, did someone mention WVO...