After four years you are almost certainly due for a new fuel filter, even if you haven't gone the full interval of 60K miles.

Also check the Radio Interference Suppression Relay. The name is misleading---it actually delivers power to the injectors. The solder joints inside them go bad after years of use, leading to weird intermittent stalling problems. If this is the case, it can often be repaired by resoldering (or just buy a new one) This relay is usually found next to the coolant recovery tank, on the right strut tower. Some later cars (including 90, I think) have two identical relays side by side. The other one powers the auxiliary cooloing fan that comes on with the AC. There is more information on these relays in the 740 FAQ.

Fuel pump relays can go bad too, in the same way (solder failure) but in my experience this is less likely.