Saskins is correct.

Here is the process I used to take off the molded air box on the standard Crossfire...

1) Get yourself a flashlight and look under the air box atop the engine, especially near the front and rear corners. Pull the L and R air tubes from the air box. These will slide off easily.

2) You will see spring metal "U" clips that are attached to the bottom of the air box.

3) These spring metal clips each attach to a rubber "I" pin at each of the four corners of the air box. The "I" pins are mounted on the engine cylinder heads.

4) Once you have located the pins and clips then pull the rear left and right pins off starting at the back of the air box. A smooth strong upward movement will do the deed.

5) Once one of the clips releases from the pin, the others will be easier to remove.

6) When the air box is removed, flip it over. You will need a TORX bit to remove 4 screws from each side of the filter air boxes. Use the correct TORX screwdriver head or you will bugger up the screws.
The Filter air boxes, once removed, will allow you to get access to the stock paper filters.

7) The K&N filters just drop in and then you re-screw in the covers and then simply reattach the air box to the top of the engine by clicking the "U" clips onto the "I" pins.

Once you do this once, it is very easy.