I had a similar problem for quite some time. I replaced the fuel filter, Volvo replaced the ECM (what a waste), and any number of other things were tried. I finally decided there must be something in the fuel tank that was obstructing the fuel flow so I pulled out the pump and discovered that the hose that runs from the pick-up at the bottom of the pump was disconnected from but just touching the top of the pump. Reattached it and no more problem. Apparently it was touching just enopugh to maintain flow most of the time but when the tank was about half full the force of starting, slowing, or turning would cause the fuel to push the hose aside far enough to cause the stalling.

Since then I always suggest checking the connections stem to stern whenever a flow problem is detected. Hope this helps.