On the Volvo engines I know with K-Jet, the wonderful PRV engine, there can be a multitude of issues if it has not been taken care of. If you can put a jumper in for the fuel pump relay that would tell you if the pump is working or not. When starting from cold have someone listen for the pumps.

I would source a good used cold start valve and swap them out and see if there is a change.

btw, the 190E is the W201 chassis.