Is this a Euro 4 D5? I had a similar issue with the car feeling like it wasn’t firing on all cylinders a few years ago; it turned out to be faulty connectors on 2 injectors. These were replaced with genuine Volvo connectors and I’ve had no problems since.
I used Vida to diagnose the problem and from what I remember, the fault description was “injector no.2 power stage signal too high”.
More info here:
https://www.volvoforums.org.uk/showthread.php?t=266805