I had to replace the power antenna in my 1990 camry, and in doing so, I had to remove this behemoth piece of ABS plastic. It is normally located on the left side of the trunk behind the faux carpet side panel, right next to the power antenna motor. It has another piece that its rests in that connects to the bumper through some sort of opening.

Of course, after I replaced the power antenna, I couldn't get this to fit back into its place. Hopefully this isn't going to cause some noxious gas buildup or something in the car. Any ideas?

http://files.automotiveforums.com/gallery/watermark.php?file=/3176/194450100_0399.JPG

At the top part of the part, there is a pass-through to another hole (you can see the lip of the other hole on the right). The entire piece of plastic is hollow.

It's a vent duct. It's rather difficult to explain the complete purpose of this part. It helps in keeping fresh air inside of the passenger compartment, and keeps pressure from building up inside the car.