You firstly need to establish if it's fuel or ignition related. When it next stalls somewhere convenient (I know, that's the problem!)check for a spark at the plugs. If OK check for fuel at injectors. However, there are a couple of quick checks to do first sitting in the car:
1. When cranking listen for fuel pump noise - it should continue briefly after releasing key. If no noise try wiggling the FPR (fuel pump relay) if you know where it is. If that fixes it change the relay or have it soldered.
2. Again, when cranking watch the tach. If it flickers your ignition sensor is probably OK, otherwise suspect it.

Hope this helps - post again if you get somewhere with it.

BillB. (A Volvo is for life, not just Christmas!)