Hi Mark,
Excuse me if you know all about the system but if not the following video is worth a watch first:
https://www.youtube.com/watch?v=otzkZ_f3Y3s
Was this done by Volvo/ Volvo specialist? It's a job that needs knowledge and some TLC.
I've just done the PCV myself with Volvo parts. My 170,000 mile car that had a smoking dipstick and a glove that wanted to take off now sucks through both holes so a few of suggestions on top of what has been mentioned already:
1. Check the PTC valve was cleaned. If it's blocked, the system won't work properly. Mine needed a good clean out.
2. Check the tube from the oil trap box to the top of the cylinder head was replaced or thoroughly cleaned. I was surprised that Volvo don't replace this as standard during the job. Mine needed a good clean
3. Do an engine oil flush and change to clean out the internal channels.
4. If you watch Robert DIY's video on this, even he tears the small rubber connecting elbow that goes into the intake manifold (drivers side). during reassembly. Worth a look as it's vulnerable.
5. Worst case - routing the pipework is fiddly and requires patience; it's possible that a pipe may have been broken during assembly as they're quite fragile.
Best regards,
Rich.