Had an exhaust noise on my 2000 5.4 liter. Sounded like a buzzing so I got under and had a look. There was a weighted cylinder attached by a clamp to the muffler extention ahead of the muffler. The clamp had rotted and it was hanging loose and vibrating against the muffler.

What the heck is this thing, what's it do and do I need it on there. It wouldn't be any big deal to clamp it back up. Just want to know what it is and what it does.

I think it's some sort of vibration damper?

Thanks for your help.