I stuck an APC filter (not exactly a cone filter, sort of a foam filter material inside a plasti-chrome material), $25 at Checker auto, on my 1.6 sentra and my high-end improved a little. Dyno tests showed +4 hp, not nearly as effective as the complete (except headers) 2.25" mandrel bent exhaut I did for about $200 a week earlier (the exhaust added 11 hp)
It is possible that without the already-performed exhaust mod the air-induction style filter may have been useless.
I would highly recomend this filter, I've noticed it is identical to the ones they usually put in top of the line greddy turbo kits. Note that all I did was seal my plastic factory throttle-body cover, remove the factory filter, and reroute the factory air-intake tube (w/ my APC filter on the end) to a location near the front corner of the car.
Worth a try. Even if it doesn't do anything the stupid wannabe mechanics will still say, "Hey that looks nice!!"
:cheers: