I had some intermittent drivabilty problems with my 1991 940 Turbo. It had the Bosch platinum plugs. My mechanic suggested that I change to Bosch Super one heat range hotter than spec. His logic was that the platinum plugs are not hot enough, and that there was incomplete combustion. Since I do mostly short-haul driving, this seemed to make sense, and changing to Bosch Supers seemed to clear up the problem (hesitation at high throttle around 3500 to 4000 rpm).

He said one of the first things he does when there is a drivabilty problem with a Volvo is to put Bosch Supers in (cheap enough). He said he wished he had a dollar for every Bosch Platinum, NGK, Champion, and Autolite he replaced that made the a Volvo run better.

The best bet is to go with Bosch for cap/roter. They are a lot better than OEM, and not a lot costlier. I got a cap and rotor from NAPA recently that was about 30% cheaper than the dealer. The box said Echlin, but the cap and roter themselves had Bosch stamped on them. I also got a set of Belden 7mm wires for about $35 that seem equal to the dealer-supplied wires in every respect. I'll just have to see how long they hold up.