xdanman; go for the full stage-1 b/c the filter's only one part of this UG. Back plate, breather ports & inlet are also modified to enhance air intake & increased flow. Also, don't forget to add a tuner so you can change settings b/c bike's already run lean from factory - gott adjust for the added air.
Might be a good time to change the look of your A/C & add some personal style - I went w/LA Choppers xXx breather & really like the look/performance. Only advice is to check clearance - I had to extend floorboards out 1" so my Right thigh didn't hit the A/C (thanks Harley Goodies).
Good luck & let us know what you choose.