The 98 should have a earlier version of the same unit as the 2000. The 722.6 was phased in starting in 96.
These are decent units as long as they updates were done under warrenty on the 98. (freewheels, valvebody and ETC.6 control unit) Some people never experience freewheel problems with the earlier units. (I think its from not allowing the car to fully stop prior to change directions) While others had problems in the first 10k.
Just be sure they were serviced around 60k and continue to service them every 60k. Make sure you stop the car before switching directions.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.