While trying to figure out why my idling is erratic, I went to check the air filter. Then screws that held the air filter housing were garbage, which I assume means they haven't worked on in awhile. So I assumed I'd find a filthy air filter when I finally got them off. But the filter was almost pure white, so I'm thinking there might not be any airflow through there. I am still fairly new to car repair so I may be way off on this one.

 

My guess is someone changed the filter recently, and messed up the screws. As long as there's no HUGE air gap in the box cover, there shouldn't be a problem.

 

I would make sure that airbox is sealed up tight. Any unfiltered air entering the engine will cause expensive problems later on. You can probably get a used airbox cheap at a junkyard that has good screws in it.
Are you sure there is no leak between the throttle body and the airbox? The engine will take air from wherever it can get it easiest, and a leak after the filter is easier than pulling air through a filter.
You might try cleaning your Mass AirFlow sensor with some MAF cleaner (don't use anything else, you will damage it). Rough idle can also be caused by a dirty throttle body or sticking Idle Air Control valve.