Just an FYI, oil through a turbo usually means oil seals in the turbo are worn and aged. It could also be related to the turbo bearings becoming worn, causing play, thus leaking oil.

Too high oil pressure issues would be an issue for more seals than just the turbo.

I am not familiar with the diesel engine in the XC90, but a turbo oil leak is the same throughout most turbos. It requires you to remove the turbo to be rebuilt. If the oil smoke is seen outside the turbo (not the tailpipe), but in the engine compartment, then check the oil lines for leaks and seepage. These too can age and its a seal/o-ring issue.

 

Second what @ChitownV said.

I assume you are seeing excessive oil in the charge pipe from the turbo to the intercooler? How many miles does the car have? Most turbo Volvos I have seen with around or over 150K on the original turbo tend to leak at least a little bit of oil.

 

In addition to all the obvious stuff, turbochargers rely heavily on "the path of least resistance" for oil control. If the return line is constricted, or there is excess crankcase pressure, oil will not drain back as easily and will try to find other ways out of the center section, i.e. through the shaft seals.