what is the air box mod and how do you do it with a piece of PVC pipe?

Also im guessing the throtle stop screw on the right of the carb is the "idle" and if I mess with the air adjustment screw which is right next to it, I can make the bike richer if i turn it in right to compensate for the air box mod?

 

I have this on my 1997 scarmbler 400 4x4. What you have to do is make a few extra holes in the air box, and you have to cut off the water boot, and put on the PVC pipe, I dont know why u have to use that though.

Hope i helped