Ok results are in - and I know you have all been impatiently waiting lol.
Went for a test drive and by the time I got back, the evap monitor had reset.
Comprehensive is still not reset but it usually takes more driving for that one so I am expecting to see it reset soon. I also decided to clear codes again so basically I am starting over again with the monitors. I do have high confidence that all is well though and this dumps all the old averaging data too and allows for a fresh start on comprehensive.

First - I have a question for those that may know.
Based on the display data in SDD, it appeared to me that the pre-cat O2 sensor is a lambda. I say this because it displays in mA and through my research, this is indicative of a wideband O2 sensor.
The post cat sensor appears to be narrowband due to it displaying in voltage from 0 to 1.25volts. This is the way SDD defaults when loading my model year and make.
What has me puzzled is the very low voltages showing up in the display for the post cat O2 sensors. Both sides are identical in that they sit around 0.04 to 0.05 volts at idle. Is it possiblel that the post cat O2 sesnors are also wideband? The graph shows both pre and post cat sensors as a relatively flat line unless I rev the engine and then I see some movement but not what I have seen in vids online with these continuous swings up and down in the voltage. Or maybe it is because I am sitting at idle? Don't know but all I can say is that both sensors - on both banks are now reading very close to one another. This was not the case yesterday when the bank 2 post cat sensor was showing higher on the graph than the one on bank1.

Anyway, I think it is fixed and if it at least gets down to only the comprehensive not completing, I can still pass smog with that single monitor not ready.
I did shoot a bunch of video that just shows my displays for various functions as I sat at idle. I am posting them up on YouTube for anyone that cares to take a look. You can see what I am talking about with regards to the low voltage readings and maybe some other interesting tidbits of information. It also shows that I am running rich on bank1 and a tiny bit lean on bank2 from the long-term fuel trims. This is something I will circle back to tackle once I get through the smog and finish up this leg of the work. Thanks to everyone who chimed in and I do hope this thread assists someone else in the future. If anything changes, I will come back to update on the post. In the meantime, enjoy the very boring videos lol.

 

The downstream O2 sensors are definitely narrow band. Their only function is to verify that the cat is working.

 

I think your almost done! Yes I agree that last monitor should set. Just give it a bit more driving time.

Yes as posted above the post cat O2 sensors are narrow band. Just a suggestion? When I replace an O2 sensor I always replace both them at the same time. They have seen identical amounts of use and abuse so if one went bad how far behind is the next one? Plus your right there and have done most of the work by getting the car in the air and removing the under body panels. There is not much work in replacing O2 sensors after all that!

Yes with time the O2 sensor response does slow down. BUT you will get a code for that if it gets too bad.
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I had the opportunity to take the car on a long drive yesterday. About 2.5 hours each way to do some business.
Once I arrived at my destination, I plugged in my scanner and this time, I had CCM not reset but now, O2 sensor monitor not reset. EVAP had reset which before the work, was not resetting no matter how many test drives I went on. So, something is / was different. I drove the 2.5 hours home and the monitors stayed as they were.
Decided to plug in the scanner and check live data for another while and the numbers are simply not making much sense to me. I then decided to plug the scanner into my Ford F-150 and witnessed what looked to be stable data coming from that computer. Armed with that, I went back to the Jag to try and make it make sense and then went for another quick spin (about 10 minutes), to simply heat soak the engine bay for more accurate readings. By the time I returned, the O2 Sensor IM had reset leaving me with only the CCM monitor not reset.
Ok, that is only one monitor and I am good to go for the smog test. I want to get that behind me as my travel permit will expire at the end of the month. Once that part is finished, I am going to circle back to trying to resolve my questions once and for all.
I know I have fuel trims that are not perfect with one bank reading slightly rich and the other reading slightly lean. It may very well add up to failing, aging O2 sensors but until I do some additional tests, I do not want to just throw money at the problem - if it even IS a problem?
It's a challenge now instead of a critical repair (meaning the registration / smog).
I have looked at dozens of videos of various scanners and testers showing very decent graphs as the engines runs. No specific Jag data but it does all make sense to me as I watch it. My car - not so much lol.
The SDD software is puzzling as the graphical displays for the O2 sensors do not seem to provide the resolution necessary to truly monitor the performance of the sensors. My portable scanner (inexpensive Harbor Freight jobber), is showing the numerical data and will graph but it is just too coarse. I may need to get my hands on a better scanner so I can really see what is going on.
Once I get through my smog, I think I will circle back to some basics and I will smoke the engine to try and isolate any air leaks that may be present. Interested to see the changes in O2 sesnor activity after I clean up somme other issues that may be happening.
So - this thread is not dead yet lol.

 

This may be why

 

That is a really good bit of intel!
Thanks for posting.

 

Hey Lads,
I accomplished my mission yesterday and the car is now CA smogged.
Had a last minute upset when I started the car and the CEL came on yet again. This time it was for a P0193 (fuel rail pressure circuit too high) and the freeze frame data on the code supported this showing 70PSI when the code was thrown. I had remembered seeing this code before, stored in my computer as I checked DTC's using SDD but it was historic. After a brief run over the forum, I discovered that this could probably be temporary and caused by the system pressurizing after it had already been pressurized. Decided to leave it as-is and started driving the car around yesterday. After doing several stops, the CEL turned itself off and as soon as that happened, I went straight to the smog station to see how this would go. Final results were a pass.
I should mention this for California owners (at least in Norcal). When I went to the smog station, I still had the comprehensive component monitor NOT reset but all other monitors were. I had not cleared the P0193 either electing to see what happened if the code was still stored but I had no CEL on the dash. Turned out that this was all fine at the smog station. I had read that you can pass CA smog with one monitor not reset and you could also pass with a stored code but no CEL. I was also curious to see if there were any visual problems as my car has a cold air intake, a aftermarket racing fuel damper setup and a heavily modified exhaust. Turned out that none of this was an issue and at least in my area, there is no sniffing of the tailpipe. He did bring the car up from idle (about 2500RPM) and I suspect it was to watch that the O2 sensor system was fully functional.
Pretty sure I will see that CCM set itself in the not-too-distant future, but for the timebeing, I am satisfied that I got the car smogged before my temporary ran out at the end of December. Once that is all settled in, I plan to go after the air leaks, etc. that I had mentioned earlier. At 181K, this car is pretty amazing. The mechanics at the shop oogled over the work I had done over the engine bay and when they saw the mileage, commented that she was indeed a "survivor".

So, I hope this thread helps others out there. I tried to be as thorough as possible and I got great replies from other forum members. It can be really frustrating for folks at times as many seek a simple answer but that is hardly ever the case. So much cause and effect going on with these more involved engines and computers and for those that wrench - as I do - it is really important to have good data to go on. Happy to say that I never threw money at this problem and was diligent to see the results of a change at every turn.

I think it is important to mention once again that cats for the 2003-2006 cars are pretty difficult to find - either new or especially used. At 181K, I wasn't about to drop 3000+ dollars for anything new to go on the car so used was my only option and it took me a solid 2 months to find the XKR Bank2 cat that finally went on the car. Remember that only Bank2 will work as the XKR bank1 cat does not have the port for the EGR tube. I did consider that maybe a good welder could cut the top off of each cat and swap the XK8 EGR portion over but never got that far. My bank1 cat still appears to be healthy.
If you are on the hunt for used cats, the secret on eBay is that breakers are listing them as "downpipes" and not necessarily catalytic converters. Maybe this gets around any issues regarding used cats - especially in CA.
Good luck to all and I will certainly try to answer any questions that may arise. Thanks again to the great folks on the forum who provided the invaluable assistance on this repair.

 

Good news!

Air leaks can erode the cats so well worth fixing when you can do so.

 

Fixed finally! Yes in Texas we also can have one monitor not set and still pass.
You really stayed with it and ran down the problems! I had no idea you would have that much difficulty finding the right cat either.
Thanks again for finishing up this thread with a success story!
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100%
Now that I am past the crucial point of getting the smog and reg completed, I can circle back to a deeper dive on anything else that needs to be addressed.
My trims are definitely not horrible with only about 5% or so trims on the worst side, I am hoping that with the smoker, I can easily track down any culprits. If not, I will be back to seek out additional advice.

 

Thanks!
If we all indeed have a love for these cars and their owners, it is imperative to create threads with as much detail as possible. I learned to absolutely hate incomplete repairs when I was part of the BMW X5 forums. I swore that I would do my best to create threads with as much detail as I could provide, even when I did something boneheaded. I think this thread goes a long way in helping others with similar issues in general but especially owners of the 2003-2006 model years who are eventually going to have to face this issue and the lack of parts availability for these years specifically.
For the timebeing, I need to transition over to my more pedestrian Ford F-150 with the dreaded 5.4L 3-valve motor.
Wish Me Luck!