Ocasional sluggishness and hesitation 99 Escort

I have a 1999 Ford Escort SE wagon 4 door fuel injected 2.0 and have recently started having a problem

Here is a history of my situation. Ran great since I bought it last June.

About three weeks ago I noticed that every so often ( less than half the time ) it started up struggling and idling very sluggish until I throttled up a bit . Then ran fine

About two weeks ago it started to go into "struggle and sputter"mode while driving through town. But no Service Engine Soon light. Parked it and let it sit overnight. Then next day it ran fine, good start up, good idle, ran great. No problems.

I ran it for small trips in town and a few out of town highway trips. One was 75 miles of interstate then stop and go through a busy city, then 75 miles back on the interstate. Not one problem

This past weekend I drove it on an out of state trip to my hometown. Almost 200 miles one way, a run that is almost all interstate including a few mountains. Then driving around in that area for two days. Still great start up, smooth idling, and good running.

Took it to a mechanic friend of mine who changed the spark plugs ( which were in pretty good shape and not fouled or sooty ), air filter, fuel filter ( which he said was pretty dirty ) checked for hose leaks, cleaned the throttle body, cleaned the Mass Airflow Sensor, ( used the correst spray ) and changed the oil. He said my coolant looked pretty dirty and that I should flush it out

When I left, the car ran like a top and I started heading back. About the time I started climbing the second mountain the car began to shake and seemed to struggle. Then seemed alright until the next steep hill, then the same thing.I pulled into a rest stop and slowed down to park and the car was struggling and sputtering like it wanted to stall.I parked and let it sit. When I got out I could smell something like burning rubber or oil leaking onto an engine. But there was none that I could see.
( I considered the possibility of a bad catalytic converter but it did not smell like sulphur to me )
The temperature gauge needle was right in the middle right where it always stopped when the car reached running temp. No sign of overheating

I let it sit for an hour and a half then started it. Hard starting and struggling idle. No surging though
. At this point I was so disgusted that I said the heck with it and started driving again, figuring that the closer I got, the less the tow bill would be.

it seemed to run ok once I hit interstate speed until I climbed a hill, then it would shake and struggle. One of the times the SES light stared blinking for about 30 seconds then stopped when I headed back down hill. Then it seemed to run ok. That was the only time the SES light came on. So it went back and forth for the rest of the ride home. Struggling, then ok. About an hour and a half drive. Had to rev up a bit at lights but I made it home and let it sit overnight.

That was two days ago.I started it the next day. Good start, smooth idle, good running. Drove around town today. Not one problem.

I had experienced something similar when I drove a borrowed pick up that would do the same thing and it was caused by the plug wires falling down close to the engine block and arcing. But I dont see any evidence of that on my car.

I had an Infinity last year with the same problem and that turned out to be a bad temperature sensor.

so Im not a mechanic but as far as I know from my research last year and this time. The list of possible culprits include a bad temperature sensor, or bad O2 sensor, or throttle position sensor, or camshaft position sensor, or manifold absolute position sensor, or egr valve, or idle air control valve, or failing fuel pump, failing fuel pressure regulator, dirty injectors, failing MAF, or clogging catalytic converter. That's as far as I know

I checked with Advance Auto and a local mechanic on getting a diagnostic test and they both said the same thing. If the SES light is not on then you wont get any trouble code. So I guess I have to start replacing things one at a time until the problem is fixed

Question. With the starting, idling and running problem being so intermittent, and since the car starts and runs so well the rest of the time, does this rule out any of the things on the list as the likely culprits and what would be the most likely culprit and the best place to start replacing?