Generally, if you wait for a "seat of the pants" symptom, you have waited too long. Inspect at least every time you do an oil change (typically 3-5,000 Miles. Visual inspection is best, if element is pleated paper or fabric it should be able to be cleaned pretty much as new...if gas or oil soaked replace. If K&N there is a cleanup and reoiling with very light K&N using their procedure. It is in the self help section.