Fuel pump relay
A 1998 940 will have the improved impeller type fuel pump, which is far more durable than the pump model used in pre-98 cars. But even these pumps eventually fail. Mine lasted over 400K miles when it finally gave up. They usually refuse to start up and do not seize during running. A good whack on the tank gets you going again until the next start.
As you are experiencing hickups during driving, a faulty fuel pump would not be my first thought.
When losing power, does the rpm needle drop to zero while the engine is still rotating? If so, you have lost ignition on the ignition coil and you should look in that direction (crank sensor, power stage).
If the needle follows the engine rpm, then there is still ignition to the coil, but the coil (unlikely) or HT leads could still be faulty. As I tend to look at the fuel pump relay as a wear part, I would start by replacing it as it will fail at some point anyway. It could very well be the cause of your troubles.
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