Take a look at the power stage, it is located on the linner fender well by the air box on your turbo car. It receives the signal from your EZK control unit and it then in turn actually grounds your coil. Not unusual at all to have to replace 1-2 in the life of a typical 700 Volvo. Past that you will need to look at the hall sensor in the distributor, those distributors need replacing every once in a great while. The seal get to where they leak so bad that the engine speed sensor is bathed in hot motor oil. If it is the sensor that is bad you can buy it seperately but rebuilding that distributor is not fun and I would recommend just buying a Bosch rebuild dist if that is the problem. It could also be a bad EZK control unit but those things rarely if ever go bad.

Mark