My 2001 S80 only stalls when I first start in the morning. The rest of the day it is fine. Idle does fluctuate at times.
I just replaced the Fuel cap and it seems to increase the frequency of the stalls. I have to give extra gas to prevent the stalls.
Is this a fuel pump issue of a ETM issue?

 

Is the car actually firing up easily when cranking? If it is stalling after firing then it is not the fuel pump, more likely fuel injection settings.

 

Sometimes it struggles to ignite, but not really. It tends to stall if I just tap the gas petal. I have to give it a larger tap to prevent stalling.