This would be easier with photos but that will have to wait for tomorrow...I was under my 01 checking out the condition of my rear brake line that runs along the body...a friend of mine had hers rust out...mines not much better...but I digress. Just in front of the junction of the hard brake line to the axle flex hose is a metal box that has some fuel lines going in and out with some rubber elbows that have seen better days. There is a metal cage over it so I can't see much...any suggestions...will post a photo tomorrow

 

That's the EVAP canister for the fuel system.

 

Evap canister is my best guess.