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1999 Mountaineer Power Loss/Backfire Under Acceleration

I have a 1999 Mercury Mountaineer 5.0L V8. It just recently began acting up. After warming up the engine goes through heavy power loss and inability to climb ANY hill. Usually cannot get above 30-35. I just recently replaced plugs and wires for a tune up and a faulty coil pack (approximately 5-6 weeks ago) causing a misfire on 8. Today in troubleshooting I attempted the “Backyard Mechanic” trick of unplugging the MAF sensor and took it down the road, no change at all in acceleration issues or on idle, truck runs the same. Unable to spot any exhaust or vacuum leaks or issues, recently cleaned MAF housing and changed Air Filter as well. All of these issues arose after a heavy ice storm, do not know if this had any impact or was just bad timing. I need help, any ideas??

If you drove it for any length of time with the misfire on number 8 you may have wiped out the catalytic converter(s). The symptoms fit.

Due to cold weather conditions, 15 or below, i can’t get a completed test on the CAT with my code reader. It is however throwing codes for Too Lean, bank 1 and 2, Still the misfire on 8, Heated O2 Sensor and codes P1151 AND 1152, so its trying to tell me lean and rich on Bank 2, which obviously doesn’t add up, but could a blocked or burnt out CAT cause this??

Your oxygen sensors before and after the cat tells the car how rich or lean youre burning and will tell the car to adjust fuel/air mixtures accordingly if Im not mistaken. If this was an older classic car my guess would be the timing is out but Im not quite sure in the more modern scenario.

I wonder, when you replaced the plug wires did you do them one by one? Same with the coils, one by one transfer of old to new as to make positive you didnt cross wires?

Well I am showing codes for 3 O2 Sensors after driving more, Bank 1 and 2 up, and Bank 2 down. I’m not for sure what to fix first, I’m my CAT is most likely bad or nearly, its an old beater and was bought from auction 2 years ago, its been taken care of thoroughly however who knows how bad it was when I bought it. As far as the Plugs, Wires, and Coil Packs, plugs and wires were changed 1 to 1 to insure no crosswire, and coils are packs of 4 are again transfered wires 1 to 1 to insure no cross.

Sure sounds like a bad cat, but with that age I would replace the O2 sensors first since they control fuel feedback for the computer.