2005 LE 3.0L V6 DOHC 24V
I had my valve cover gasket replaced and not long after I started getting a vibration sound from the engine compartment. I was looking around yesterday and saw this:

I stuck a piece of foam behind it and the vibration is gone. Can someone tell me what it is and what it does?
I need to go back to my mechanic and have them do what it takes to make this right.

 

Looks like a bracket of some kind. Any more pics of it? I would like to see what the bracket is attached to and what part of the firewall it is connected to.