You haven't verified if the noise goes away on diesel purge. You also haven't verified if it gets louder with RPMs. All I hear is a rhythmic knocking and have no clue what I'm listening to.

So I can't say anything until either of those are answered otherwise me and everyone else will just talk out of our hind-end.

I can say this.. If it goes away on diesel purge, it's a fuel issue. If not, it's something else internal bottom end or top end. Ever run it out of oil or low?

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k