Leave it alone.
There is almost no difference in performance in all the tests I have seen and K&Ns can dust engines although David Vizard says that on a petrol engine the inlet pulsations will ensure no dust gets through. And Vizard is pretty well the guru on most things petrol related. He also claims they are no good on diesels as there are no inlet pulsations.
So it shouldn't do much damage eg dusting but will not do much good either. The pressure drop over a clean filter is very small and usually the design of the airbox is more important.
Regards PhilipA
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