There should be a prefilter on the outside of the hood.
If you look closely at the foam inside the airbox, you will notice the air doesn't go through the foam. By removing the foam, the only thing it will do is make the sled louder (howling from the carbs). Just leave the plastic shelves and dividers alone.
What does taking out the dividers and shelves do? I gutted mine and wondering if I should put it back in? I thought I'd get more airflow if I gutted it?