k&n filters may 'tune' sound, nothing more than that.... open filters will actually decrease power as hot air from bay is getting sucked in instead of colder outside air.....
1.8 AAM, ANN with 75hp, ABS and ADZ with 90hp engines are useless for tuning to get more power. single point injection and so on.....
yes you can get more power but that involves new downpipe (4-2-1 or GTI pipe), new cam, etc but that may only get you to about where a well running 1.6 100hp is to begin with... was playing with that thought when swapping my 2.0 2E for a 1.8 AAM but it's just not worth your money....