The chimney folks came-out today as did the second tech per my previous post. The chimney is in the same condition as when it was built in 1952, meaning there is no wear or damage. However, they noted it has a number of turns, etc in it and are providing a quote for lining the chimney as an option to produce more consistent venting. They would need to break-out brick around the chimney, etc. The quote for that job was $$$$ and it's a lot of work. I was impressed with the chimney crew, it's a multiple day job.
The conclusions to the problem seem to be the following:
(1) Carrier inducer motor performed for about 10 years at top performance and other than a few DSS resets the last few years per my previous note, the unit operated. It became more flaky recently. Apparently a straight RPM measurement wasn't enough to detect the problem. Simply removing it and putting it back-in, per my previous post, appeared to change the performance of the unit. Don't know why-- bearings, orientation on axle due to bearings, don't know. Lesson learned-- RPM measurement alone may not be enough to diagnose a bad inducer motor, perhaps the RPM was changing at points in-time not being measured or there are other factors in alignment, etc. Again I'm not a pro, I watched the pro's try to figure it out, and they themselves couldn't explain why.
(2) The inducer motor coupled with chimney flue adapter and the turns in the chimney does create "more work" for the unit and as others have said. However, no CO leaks were ever detected anywhere in the house (detectors in multiple areas of the house around chimney and elsewhere.) Nor did any tech working in the house ever detect CO.
(3) It appears that replacing the inducer motor will bring the unit back to where it was in performance; however, lining the chimney would help if venting out the chimney.
(4) I didn't get quotes yet, but if I want to replace this unit in the future with a high efficiency, as I understand it in this area they don't vent it in the chimney, they vent it out a back wall.
If anything else is learned, I will update the thread. THanks again fro everyone's help.