How long has it been in the car? I generally clean mine every six months which is technically, too often if you go by K&N's standards. They say as the filter gets dirty, it actually cleans better (I'm assuming this is true to a apoint.) If you go to your local Auto Zone, etc. they will have a K&N filter cleaning kit. This comes with a spray cleaner, oil, and instructions.
Ya, it will clean better, because it will create a smaller passage for the air to come through, therefore catching larger particles of dirt. But, with this "cleaning better" you are going to lose performance because the air passages are getting smaller at the same time..
I have had the car for 2 1/2 years now and I have never even touched the air filter, it is inside the inner fender. So this will be a first time for me. Before then I have no idea how long. That's great, I will pick up that kit this weekend.