Running a pipe cleaner through the manifold vacuum orifice, and then through the small hose to the flame trap housing would be step 1. Are you sure your guy didn't already do this?

Replacing that dip tube is a horror story, for sure. I can't imagine a kink, but also don't understand why it didn't fit the bore. Volvo's part suppliers aren't in business to keep 30-year-old cars like new, perhaps, or maybe the tech didn't want to risk a broken wire from a wire brush down the bore. Then there's that clamp you need to have the oil pan off to reach! Yikes.

In the end I think your idea to blow test it with separator removed is just what I would do.

Sadly, depending on the car's oil maintenance history, you might just be at the point where the rings are not containing the blowby they once did, and even when the PCV contraption is at maximum performance, the gases those rings pass are too much for it. I've read of many stop-gap solutions from increasing the manifold orifice bore to ditching the PCV for a catch can. Main thing you want to do is be certain where your car is on this scale.


--
Art Benstein near Baltimore

http://cleanflametrap.com/pcv_test.html