Everybody running K&N's has a MAF sensor. My Mazda had one for 100,000 miles with no issues, cleaned & re-oiled once. The cleaning instructions are specific for not screwing up your MAF.
Jim has it right here. At less than wide open throttle (WOT), the ability of the air filter to pass a large volume of air is irrelevant: the biggest loss of airflow is the throttle. If you let in more air through the filter, then the throttle just closes more.
This is all managed by computer...