OK, so I'm poking around under my hood today, trying to familiarize myself with all the various stuff under there. There's a small canister on the passenger side near the firewall that has what appears to be a small air filter inside of it. What is this? I can only assume it's some sort of cabin air filter, but I don't know. Also, in the cab, on the dash to the left of the steering column, there is a flat black filler plate that sticks out from the dash a little bit. Upon removal, there is a rectangular opening, and a slightly recessed round opening. What is this? I can't even begin to guess what this is for.

Also, mounted to the firewall, there is some type of button that has a rubber cover over it. Any ideas?

 

Sencondary air injection pump under the hood is my best guess, ive pulled the cover of mine and cleaned. its a little foam filter. and the other from what i gather is just an option plate, maybe where the SLS button would be. or something the previous owner had installed.

 

Yes the first is your secondary air.
The second sounds like a blank, a spot open for other factory buttons.

 

I didn't think about the secondary air. My other vehicles with it have not had their own secondary filter. I figured the plate was for a factory option, I just wondered which one. I think I've figured out through RAVE that it is for headlamp leveling. Weird thing is, it seems like the mechanism is there, it's just not hooked up. ?