2000 S80 2.9 auto Misfiring

[f o sullivan]

I have a 2000 petrol 2.9 auto S80 which is misfiring and I would like some help diagnosing the problem. I had the ETM fully replaced last June following an unsuccessful software upgrade shortly before that. The local Volvo garage recently changed all the plugs hoping that would help but it hasn't. The strange thing is that it usually happens below 1000 or 1200 rpm. Occasionally if I try and drive it hard past this point it will continue to misfire at higher rpms but generally it will clear itself at around 1000rpm if I let it run without too much pressure. I have read that changing the ignition coil in the offending cylinder might help or alternatively I could try fitting a full set of leads.

Help!! All advice greatly appreciated.