Check this video:
The studs on mine were removed and replaced with bolts before I purchased the truck. They were looking rough so I replaced them and the gasket just to be sure. I've heard it is very loud.
I did 2 things, and it seems to have gone away, or been greatly reduced.
The first thing I did was a couple heavy doses of injector cleaner coupled with working it hard towing the camper.
The second thing I did was GDE hot tune, emissions intact.
I also replaced idler pulleys, tensioner, and...
I also just noticed this, did you ever figure it out?
I compared with my dad's EcoDiesel, and we concluded that his does it too, but not nearly as loud. I replaced dpf/scr flange bolts and gasket as preventative maintenance, and was hoping this might help.. I found that mine had already had...