Rattling Sound

Hopefully I can get some sort of answers from anyone on the forms regarding what this sound is. I've been to one dealer twice and they weren't able to fix it and another dealer recently that said there were just rocks on the heat shield. I had high hopes that the sound was gone, but was let down again .

I've uploaded a video of the sound below. It basically sounds like a metal rattle sound and only begins to appear once I reach speeds above 60mph. (Being a daily interstate driver, you...

Rattling Sound