Ok, the sensor might relieve the pressure at idle but would not at highway speed. You should be able to use any gauge for the test, there won't be any airflow so the gauge won't get hot. The problem is the tubing, it will get hot being connected to the exhaust. Do you know what a manometer is? You can make one easily and compare backpressures. .I am beginning to lean toward some sort of ECU issue. Can you summarize the components you have replaced with known good components (not new unless you have put them on a different car and verified they work correctly)?

 

Can you describe how it runs when the MAF is unplugged?

Checking exhaust back pressure only takes a few seconds, so the exhaust system doesn't need to get very hot. Clean cats will have an equivalent flow path nearly the same as the 2 inch pipe, so opening the upstream O2 sensor port will have very little effect. Maybe at idle like Extinct mentioned above.

The O2 trends look good. The quality of bank 1 is definitely different than bank 2. Have you checked the signal from the TPS? (can be done with the scanner, key on engine off). Have you checked compression?

 

Update,

Finally solved my not running, rough running, running and stalling problem. Well, not me, but rather someone smarter than me

Sucked in my pride and took it to a former Land Rover tech here in Austin who now does private mechanic work (first time in 25 years I paid someone to do anything to a car other than tires and inspection). had to drive it to him late at night the 10 or so miles in order to not impede traffic, as once I got it to idle without feathering or other throttle work (usually about 5-10 minutes, first at 2,000rpm+, then slowly down to 1,000 until it could hold idle on its own without stalling) I could go over 50-55MPH and 2,200 or so RPM lest it die at anything over that, and then I would need to wait until it cooled down completely before it would even start again. Mechanic couldn't figure out how I was even able to get it to do what I managed to do as he had to tow it into his garage once he was ready to work on it.

He discovered (with whatever tech tools he had to detect such things) that my brand new Bosch coil packs, wires and plugs were only producing 25-30kV spark, instead of the spec'ed 50kV.

Hypothesis is that the harness extension wires in the coil relocation kit I installed 5-6 years ago might have over time developed more resistance over time, so the coils were not getting enough juice to generate the required voltage.

He de-relocated the coil backs back to the back of the engine, did a little firewall hardness repair, and now it runs great -- and does about 5mpg better (previously 11-12, now 16-17).

What's interesting is that it didn't generate any misfire codes at the outset of the well-documented problems I outlined at the beginning of this thread.

So now I have a well-running engine with new coil packs, wires, plugs, MAF, CKP, CMP, TPS, ECT, throttle body, fuel pump and a bunch of other stuff I threw at it over 2-3 months that I can't remember. Good for another 100K miles :-)

BTW, anyone want to buy a lightly used Coil Pack Relocation kit?

 

Thanks for the update! Glad you are back on the road.

Maybe a different hypothesis, since copper wire does not change resistance, but the low voltage connectors/splices/crimps could have gotten rusty or corroded. That would provide less than primary voltage. If spec is 50 kv and we only got 25, the primary voltage would have been only about half of normal, 6 or 7 volts. Of course long, small gauge wire on the primary also causes voltage drop.