If it's not a turbo, it must be Regina FI with REX ignition, and the REX is not known for Power Stage problems. However you might remove the coil module (2 torx screws) and clean the two studs and contact springs. See pics below.

REX Coil


Coil Contacts


"it will die while running at highway speeds. It simply shuts itself off. It does not miss, spit or sputter....Usually, i pull over,put car in park. and turn key off, & it restarts immediately & runs fine until it does it again."
• That sounds like a variation on my RSRelay grounding failure. For more (including pics) see THIS POST for pics and a link to my "Puzzler Post" with more symptom details.

"...CHECK ENGINE LIGHT IS ALSO ON"
• You mean all the time, or when the stall-out occurs? In either case you should get the OBD codes to see what's causing the CEL. See OBD code info in the 700/900 FAQ, under the --more-- menu at upper right.
Post back with codes, if any.

BTW, 22 mpg is on the low side. I'd expect 25 to 27 depending on driving conditions.



--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.