I have a couple of suggestions:

You might want to look into a fuel system cleaner....it's possible than the fuel injectors or lines are a bit clogged, or that your throttle body needs to be cleaned (if you want to check this, you can always take off the hose that connects to the throttle body and just look at the top of it...if it looks dirty on the outside, it's probably dirty inside too, if it looks clean on the outside, it's probably not too dirty on the inside, etc.

Also, you may look into when your fuel filter was changed...although I believe Volvo recommends a change around 90 or 100k for the 850 (don't remember which), that's far too long...if your fuel filter hasn't ever been changed, definatly do so! Filters are cheap $20 or less. There are instructions at www.volvospeed.com if you want to do it yourself. You'll get better gas mileage too.

Just for assurence you may want to check the condition of your plugs, but I wouldn't say that's the highest priorty cause.

Also, if you are having Idle issues in addition to this, check your vaccum line elbows (again, instructions at www.volvospeed.com).

Since your problem seems to be predictable with a new fuel pump, I would go with filter change and fuel system cleaning before anything else. I don't know what fuel system cleaner they use at the dealer's garage, but I understand if you can find out the name of that, that it works pretty well. Also, try not running your car down to 2 gallons for a few days and see what happens....over the years sometimes junk builds up in the bottom of the gas tank, causes the car to run alot worse on a near empty tank...but I doubt that alone is the cause (especially with a new fuel pump).

Keep in mind your symptoms could be a combination of problems coming together...IE bad spark plugs and a dirty fuel system, etc).

Also, you might want to check your engine codes in the dataport near the washer fluid fill...sometimes codes are stored without the check engine or other warning lights coming on.

Hope this might help, I know you frustrating stall gremlins are ;)

Brandon
95 854T 89k