Need Help Identifying missing part?

My assistant ran over a dead dear in the road and there were a couple wires and a tube left dangling from the car just in front of the gas tank. The check engine light is on, but otherwise drives normally.

We looked under another mazda tribute at lunch, and there is a large black plastic box which is apparently missing!

Any idea what the box is? I'm assuming its smething to do with the emissions system, since such a large piece is missing and the car seems to run slightly better with it on the side of the road somewhere.

Any help is appreciated.