First off, thanks for maintaining a darned useful site!!
 
A few days ago my 95 T5 with about 145,000 km started stalling from time to time from idle. No indications, check lights, nothing - the engine just stopped. First few times it restarted OK, but rapidly got worse and then wouldn't start unless the throttle was opened (as if it was flooded). 
 
Research found your item on sudden stalling http://au.oocities.com/ozbrick850/engine-suddenstall.html and a few other resources including this: http://brickboard.com/ARCHIVES/1997OCT/4307.shtml and this: http://www.volvoclub.org.uk/850reg.htm.
 
I was relieved to find a likely culprit when I saw a very dirty throttle body. In my case I'm about 99% certain that the problem was a well gunked throttle body that had gotten to the point where there was no air bleed through the very small gap left when the butterfly is closed against the factory set stop. I gather that some oil must get past the turbo seals and into the inlet airstream and residue builds up in the throttle body and especially around the periphery of the butterfly in its closed position. No air getting through also helps explain the apparent flooding and only starting with the throttle opened.
 
Removing the throttle body was dead easy and 15 minutes with a toothbrush and engine cleaner had the assembly looking like new. I did take the throttle position sensor off the body first to make sure it didn't get damaged by the degreaser or rinse water. Probably the trickiest part was figuring out how to release the locking clips on the electrical connectors (throttle position sensor and one other).
 
Since cleaning and reinstallation I've had no more engine stalls. 
 
The throttle body was cleaned on car during an independent Volvo specialist service about 20,000 km ago. Don't know how well that was done (and I sure hope I don't have a turbo oil leakage problem) but cleaning it off the car was both easy and more certain to get a good job.
 
Hope this is useful. 
 
Cheers
 
Al Dally
Canberra