The turbo is glassy smooth, when turned by hand and I can't feel any play, either laterally, or thrust. With 15-40 Castrol in there, I didn't expect it to spin "like a top" with cold oil, and it didn't.
I need to get under there and check the exhaust system. Right now, the only thing I know for certain, concerning the noise is, it's louder than it was a few weeks ago.
So, for turbo experts: What are the chances of a very smooth-turning turbo, with no discernable play, being bad? Bear in mind that the noise I hear is not as loud as the the diesel rattle from the 6.5.