I have about 70,000 miles on my S80, and the fuel mileage has dropped significantly, so I think that it's time for a tune-up. I have a set of spark plugs for it. The front bank of cylinders will be a piece of cake, while the rear bank is more of challenge, but I've done worse. My copy of VADIS only mentions a torque spec (25 nm) for the plugs. I can't find a gap measurement. (Maybe that's my fault) Are the Volvo plugs pre-gapped? Do I need to be concerned about it? Thanks in advance!