Whatever that ppl attested to performance gain, there are generally 4 types of filters material, paper/Fiber (stock), foam, gauze and cotton and finally steel mesh filters.
Of these lots, steel mesh are actually the first type of filters used since the 60s and abandoned....why abandoned by car manufacturer, cause the filteration levels are extremely bad, letting lots of contaminants thru, performance increased initially due to massive amt of air going thru (oiled or not) but in long term, performance will drop drastically due to dirty throttle, etc. Not worth the dime.
Foam and Gauze have abt same filteration levels, both much worse than stock paper. Performance wise, gauze/cotton, gives the best performance while foam
is only slightly better than stock.
So conclusion is the basically the poorer flowing filters, remove more particles and the better flowing filters remove less particles fact. In actual fact a good stock paper filter does not inhibit flow as much as you think. Based on Bob the Oil Guy testing, the best gauze filter (K&N) produce a "WHOOPING" 0.14% better air flow than stock paper. For a high performance engine going on high speed, this percentage makes a bigger and noticable difference but for our standard street car (ie. PE), I really don't know if you can REALLY feel the 0.14% increase in airflow performance or not.
Based on this basic knowledge, I forgo changing any performance drop in filters for any of my cars unless I get myself those GTR-level rides. My priority is the best maintained engine for long lasting performance, so drop in filters is never an option for me.
wah lau....so I wasted money on the Works filter then....