K&N
Who has replaced their stock air filter with a K&N? Are they really better? Improve performance, gas mileage, etc.
Forum Discussion
I've used them for years on off road vehicles. They filter all particles out, especially once they get a bit of dust on them. They're not supposed to be sparkling clean. There are also pre-filter socks that fit over them for extremely fine dust, but these are rarely necessary. They don't provide a noticeable increase in mileage, but it seems like smaller engines feel more responsive to a throttle change. If people claim they damaged their engine or MAP sensor, that's a bunch of malarkey. It's coincidence. Sort of like claiming that you got a flat tire because you put new floor mats in. The filter will definitely save you money in the long run.
