On my 2001 5.4L F250 air filter, there is an arrow printed on the back of the rubber circular edge. It says "align arrow with notch" then points awkwardly toward the edge of the rubber circle. I thought maybe they meant the top notch of the plastic shroud but when I go to join the back part with the front part and clamp them, there is another picture showing "arrow placement" on the black plastic piece that mashes down on the rubber backing which is attached to the intake hose.

What arrow should match what notch? Furthermore, why? And does it matter which directioin the circular filter is installed with regard to rotation?

Help!

 

I've never heard of issues with regards to which direction they are installed. As a matter of fact on several applications I've used it to my advantage, ever couple thousand miles changing the direction because it tends to load up in one area if you don't.