I chased a stalling at low rpm problem for longer than I will admit, and finally asked a local indie Volvo mechanic in my town (Jim Stevens in Cincinnati) And told him all of the things that I had tried to fix the stalling and he suggested the CBV also called the blow off valve. I was skeptical, but desperate enough to try anything at this point. And sure enough mine had a 1/4 inch hole in it! I just wanted to post this to help anyone else chasing this problem.

I found a used diaphragm on TB and even though it was dry rotted and had some cracks (seller didn't know, and made it good), none of them were through to the other side. It worked, no more stalling! (I have since found another used one with no dry rot or cracks) Here are just a few of the things that I tried ...

Checked all OBD codes, and it is not spitting any codes.
Cleaned throttle body
Cleaned Idle control motor. Also swapped it out with a known good one from a perfect running 240 (same part#), still low idle, and stalled again
Changed out fuel inj. relay (before I realized it is idle related)
Changed out RSR relay " " " " " "
Checked every possible spot for a vacuum leak
Changed out AMM with a known good one, still stalled, same symptoms
The car has a new Crank sensor
The car has a new Power stage module