Problem solved!

Recap: 850, 170k, owned since practically new, almost everything original.

Ran fine for forever, then sudden onset of intermittent loss of power/sputtering. Poor running lasting several seconds then back to normal. Would stall if at idle but restart after a few tries. If at speed just lost power then came back.

Pulled (almost new) plugs: black soot on all of them. Also noted soot blasting out of tailpipe when I started the car.

No CEL (later found to be burned out). Got code reader; no codes other than secondary air pump.

Lots of good suggestions: fuel pump, fuel pump relay, fuel pressure regulator, fuel filter, MAF sensor, O2 sensor, cap/rotor/wires/coil, idle-related stuff, vacuum leak, probably a few I am missing. All good suggestions. Unable to prove any.

Used OBD app on iPad and watched signals as it drove good/bad. Nothing I could see different. Dang! The car is stingy with the clues.

Checked for and found no vac leaks.

Time to start replacing parts. Since it seemed the computer could not tell anything was wrong I started with the coil instead of sensors. Lucky guess! Running fine with a new coil.

Lots of good help. Will follow up on maintenance items to head off future problems.

Thanks to all,

Terry