what is this???????
 

what is this part and what does it do? i am getting a loud clanking sound from it and the truck is idiling a little rough. 2002 3.0 6cyl. 82000 miles.

That is the Resonance Flap/Manifold. Without getting technical, the flap opens or closes to provide increased torque at low rpm's and additional power at high rpm's.

Rob_

does it go bad? would it have anything to do with rough idle or tripping codes?

It can go bad but very rare that it does. It may cause a rough idle if it is leaking or stuck. Do you have a check engine light on?

Rob_

yes.

You'll need to have it checked at a dealer or indy. You need to find out what faults are set if you were to attempt a DIY.

Rob_