Thanks Dave, but I think the explanation for this is a little too simple... ![Shocked :o](http://www.cvoharley.com/smf/Smileys/CVO/shocked.gif)
The factory air filter Stock on your bike will work. That said, you will be leaving horse power and torque on the table. This is because it does not have enough air flow. On motors over 120 Horse power, going from that filter to a true high flow filter, you will pick up 3~5 horse power. Most any tuner worth his salt explain this, and even better yet prove it. The kit includes a high flow intake, bigger throttle body (for more air flow) and new heads for Higher air flow. New exhaust for increased air flow.
Why keep a filter that is not increased flow when everything else is increased air flow?
Me if I am spending over 3K to build a motor, I am sure not leaving power on the table. When the 131 kit came out two years ago, Harley recommended the extreme flow ventilator or extreme flow heavy breather. Its not listed this year with the recommendation for it.