I put a stock K&N filter in mine and am very happy with it. As usual there are many factors with the K&N and also the "stock" paper filters. Proper cleaning and oiling has to be a major one of these. That, in itself, will determine what kind of filtering performance you get from a K&N. I personally think some of the so-called tests, which do not even mention this, could be slanted in any direction for the results you desire.
No filter is a cure-all or performance "upgrade"
and opinions for brands will be argued till the automobile is no more. More importantly, proper and routine maintenance is the bigger factor.