well, the stock filter housings do work, btu they are very restrictive and the foam elements are junk.
Just adding a high flow filter will give you a little improvement in power.
It's been proven that getting more air into the engine will give more power.
of corse sometimes this will make the engine run a little leaner so jetting up (to richen the air-fuel mixture could be a possiblilty.
there are bolt on air filter kits for cars (k&n) that will give you a 24-50 horsepower increase.
I know, it sounds impossible to gain that much from changing the air filter & housing, but they have proven dyno results.