11 Avalanche, 180k miles, automatic, 2wd, 5.3l,was throwing O2 sensor code on bank 2, cleared that. Changed both downstream and upstream O2 sensors on bank 2, no difference.

Has clean air filter, good exhaust flow (took to exhaust shop in time before immobilized when I could feel that my power was tapering off. At that point I couldn't outpace my 99 yukon and was clearly diminishing in performance at a steady rate. The shop pressure tested and gave me green light for nothing being clogged), performed my own exhaust pressure test. same results.

revving engine will produce inability to hit higher rpms but if you pull an O2 sensor and leave the hole open, you can hit the rpms. I don't know about it's ability to drive like that though, as I did not attempt. But the throttle activity with that change leads me to think the fuel pressure should then be fine, but am going to pressure test for certainty tomorrow. (sunday 19th Nov).

what happened when it finally quit? I was getting on the freeway at an incline and hitting about 70 to 75, I had just finished clearing the o2 sensor code on a scantool as I was merging and didnt go maybe a quarter mile before the engine started dropping power and acting like she had clogged exhaust. I pulled over, she continued to idle for me for some ac (thank god #phxsunhot) but would not move with any confidence. I was able to limp it about another 1/2 mile at maybe 10mph before she wouldnt do that anymore and wanted to die. towed it by straps home and now all she will do is move around on flat ground when I need whats behind it.