http://www.knfilters.com/filter_facts.htm#WORDI have used K&N for along time and love them. I have never noticed any ill effect or had problem. I will say that when looking at a paper filter and a K&N filter the paper filer has more dust and dirt on the surface. Wash a K&N and you will see how much they really stop/hold.
Let us also look at surface area. it is common for a K&N filter to have more surface area/air flow then a factory style filter. so all things being equal at 99% filtration(cause nothing is 100%) the K&N filter, yes will let in more due to the added air flow, but is still offering the same qaulity as the factory one.
IE - A facoty filter flows 100 Cubic Feet of air per Minute "CFM" and lets in 1 partical of dirt. The K&N filter flows, 200CFM and lets in only 2 particals of dirt. So yes it let more in, but had the same amount of air flowed in with the factory filter it would be the same. given you more air flow for your airpump(engine).
Now everything i look at says a factory style filter can be as low as 93% effetive and K&N says they opperate at 96-99% effective. given you even better odds.
So is it worth it. I think it is. Given the amount of dirt we throw at them the filter, evn a paper filter will fail and easly clog/let particals in. i think a pre filter would be a good idea regaurdless of what type of filter you have. and over oiling is a user error and can not be put on K&N but the user
