Normal or should be worried??

[JMBT]

When I pulled the air to air tube off the turbo, inside the turbo compressor outlet was a light residue of clean oil. It was just a residue, no actual oil sitting there. It was only in the compressor side outlet and not in the pipe or CAC inlet.
I visually checked the turbo and it looks fine. I also checked the radial & axial end play and they are fine as well. Turbo only has 180K and was brand new from Cummins not reman or aftermarket.
I wonder if this has anything to do with the exhaust smoking a bit after I have idled to warm up? Could turbo be pulling a bit of a vacuum at idle and sucking a bit of oil into the intake?