The Cabin air filter is located on the passenger side behind the glove box. You access it from under the glovebox.
Step 1: Remove this plastic panel. It is held in by two T-25 Torx screws. Once you remove the screws you need to give it a pull down to release the clips.
Once you remove the panel you will see the following. The Cabin air filter is located in the area circled in yellow.
Step 2: Remove the following hose. You need to remove the T-25 Torx screw and pull out the hose/plug.
Step 3: The cabin filter panel has two of these locking mechanisms holding it in place. Give them a gentle turn and they will click to lock and unlock. Unlock both and pull down on the panel. You may have to give it a slight tug to get it to pop off.
Step 4: Victory! Once the panel is removed you can pull the filter out and replace it with a new one. Be sure to look at your replacement filter to see which direction you need to install it for proper air flow. In the photo you can see the dirt/debris that fell out when I removed the panel and that is only after a few months so its a good idea to replace them.
Repeat the previous steps to put it all back together and enjoy cleaner air.
The part number is: 31407748. Its about $25 on FCP euro and backed by their lifetime replacement guarantee.