I just recently put the ipd PCV kit on my 97 850 T5. I read through this site a lot, got several tips, but couldn't convince my self that there wasn't a blockage in the PCV. I didn't want to tear into it without the ipd kit handy, though. So as I disassembled, I checked everything for the tell-tale signs of blockage, and found none. I blew through every tube, and though the small ones had a lot of air resistance, so did the brand new ones in the ipd kit. I broke one tube getting it off, the curved one back by the turbo intake. I went ahead and put the ipd kit on and threw out all the old parts. Felt like I hadn't accomplished much though. While in there I found two cracked vacuum line to the turbo controls, wastegate maybe, and not sure what the other was. I replaced those just because. I also put a new oil filler cap on, so the seal was new there.
Damned if that thing hadn't leaked a bit after that, even though I didn't think there was any blockage in the PCV. Maybe it was also the turbo, my wastegate may not have been kicking in, so maybe overpressuring the whole system. I've been running mobile 1 for about 60k miles, that might have impacted how unclogged the PCV was. The engine seemed leak free until I took it on a 4 hr roadtrip, now there's oil all over the rear of the engine and turbo, none on the top or front though.

If you can get the little curved tube out of the fitting near the turbo intake, and verify that's not plugged, or clean it, that seems like a place to clog. If you feel like pulling the separator box, you can figure out if anythings clogged, it's just darn hard to get to it.
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past volvos: '80 242DL, '88 740GLE, '86 760GLE. Current: '97 850 T5