For those who have opted to keep the filter box on your S14, you will probably know well what a bitch it is taking the top off. Three clips are easy to deal with (the top one and the two along the long sides), but that bottom one!
You can see the clip in question in Figure 1.
Removal is easy. Just push it off using a screwdriver (Figure 2).
To re-seat the clip, use a piece of wire to hook over the clip (Figure 3).
Then pull the wire back over the filter box (Figure 4) and voila! Easy when you know how, huh?