Michael,
In older Volvo's 850 and 960's there is something call a power stage that controls the coils. On the 850's with a single coil, the power stage is on the ignition coil assembly Vs the 960 with direct injection no cap but 6 coils. This car has 2 power stages one for even number of cylinders and the other for the odd number.
Since your car has miss fires on all cylinders look into this as a possibility, not sure where it might be located on your car. 960 power stage is on the intake manifold by the front and rear side.
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