Volvo Repair: 98 S 70, fuel filter, s 70

Question
My 98 S 70 which has around K90 miles stalls without any warning.  Doesn't happen all the time but it's getting worse by the week.  I can let it sit for couple of minutes and  start back up.  I have left it with the repair place for days and they can't figure it out because nothing registers on the computer. They did change the fuel filter and think the pump is malfunctioning. Please advice.  

Answer
Ah the ol Fuel Filter trick.  Why does everyone think that solves everything?  I have never seen a Volvo Fuel Filter clog.  Anyway, The fuel pump may very well be the culprit but it has to fail in order to be 100 percent sure.  This is a common failure on the 850/70 series.  I would also change the fuel system relay when you change the pump assembly.  Roger