I see this is an old thread but I had a 51 plate 2.0t 5cyl Volvo in today, (s60 I believe) with a misfire that brought up codes :3503 misfire at least one cylinder & 3543 misfire cylinder 4. (read with verdict). I swapped no.4 coil to no.2 & plug to no.1, cleared faults & road tested. Same codes returned. Turned out to be no.5 coil, thought snap-on had got the definition wrong but now also thinking volvo may be using firing order (as Glen said, 1-2-4-5-3)