My 98 Volvo S70 hesitated when starting this morning and I had to give it more gas to keep it from stalling. It ran fine until I turned it off and then when I started it again, it hesitated the same way and then the check engine light came on. I plugged in a diagnostic checker and it showed Error P0003 "Fuel volume regulator control circuit low"

Any idea what this means or what I might need to do? Could this be caused by bad gas? Coincidentally my son filled his car at the same gas station I did and yesterday he started having problems with the engine idling too low, and then after an adjustment was made at a service place it now idles way too high.