Low boost could be due to leaking CAC or the related hoses/clamps.
I can't see there being enough copper (in the bearings) of a Turbo to show up in the oil sample and still have a functioning turbo. I had high copper (96 ppm) in my oil sample too and it was suggested that it could be from normal wear-in (not knowing how many times the oil was changed by previous owner since the coach was new) or from the oil cooler (Blackstone said to just change the oil and send in a new sample after putting some more miles on engine).
On the Turbo - If you can remove the intake hose to the turbo, you can reach in and grab the turbo spindle to check for movement. Any up-down or in-out movement (more than a few thousands of an inch) or visible scoring on the housing would indicate the need to replace it. You would not want to wait too long to diagnose this as a turbo failure can send metal into the engine and then it gets much more expensive.