K&N filters allow more dirt. Just saw this on one of my other forums and thought I should pass the link on to the test. It seems that the K&N air filter is not the best, or even close to it as far as filtering contaminants. Or increasing HP. Here is a link to the tests, http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm I really haven’t read threw the entire article but the graphs show more the words anyway. So seeing we are truck owners and this is an important part of fuel economy and engine longevity. I thought I should show the tests.