K&N = lower efficiency than ANY paper based filter = more dirt in engine = more wear metals. K&N has no place on stock fuel injected passenger cars.
Your extra airflow through your filter is still restricted by the same heads, same cam, same exhaust, same intake plumbing, same engine tune, so its not providing any extra power unless you're modifying other parts.
Don't get me wrong it filters OK, but we are here for the best right? I would rather have a K&N than running filter less but filter technology has changed and cotton gauze needs to be retired.