Well its as Serious said he mentioned the oil and cotton make up and yeah ensuring that you replenish the oil on the filter will ensure no dust going in.
Btw. what managment systems would be used on the throttle boddies.. What I mean is what else would be changed to ensure they are efficently used etc...
I fitted one on my old mini after I bought it and then got the carb set up properly for economy use, first time I cleaned the thing was five years and 40,000 miles later and it didnt really need it then. Totally out performed the original paper one. TBH a K&N should outlast the lifetime of a car and then some if you look after it.