of cos i am very sure. before i went into car modding, i heard all these stuffs, open port high FC, auto gear not suitable for straight flow exhaust, VS & grounding can increase power blah blah....the lesson i learnt, actually until u tried out all those mods urself dont draw conclusion as others told u. Now i understand all these stuffs only after i tried out myself.
Frankly speaking, u will only noticed higher FC after u bump up ur compression, change high cam, port polish & retune the ecu. Now my 1.8L RM70 only can go 250km.

i washed mine, but must spray from inside out & leave it to dry. only can use water not air pressure

i read in an article, actually drop in filter wont give u extra hp or torque gain. Since u just put in the filter box, it still remain as restrictive as before, the slightly better flow of filter wont let u gain much. open port still way to go with proper heat shield and cold air intake.

last year or 2 years ago, hypertune got an article on it. Of cause can proof, buy a new drop in filter can run on dyno lor.