Low Power Up Hill Still after plenum replace and cat inspection

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Junior Member
Jun 28, 2021
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2001 Dodge Ram 1500, 5.2L with 46re trans 96k miles
After reading a copious amount of posts on here over the past few years and learning a lot, thanks to all of you!

Need your help once more, still low power up hill.
It seemed to have gotten a bit better after plenum change along with a few other intake manifold parts replacement however problem still persists.
Which leads me to possibly still vacuum leak? (tried checking for with propane around lines) probably need to properly do it with smoke.
Maybe Torque Convertor? No other signs of issues with TC though. Seems more of low rpm lack of power and not high rpm without acceleration but unsure.
Shifting seems okay, no slipping and mostly properly down shifting at appropriate times up hill with OD off.

As far as the parts I've replaced or checked over the past few years and only put on 6k miles
-Plenum and intake manifold gasket
-Borescope inspection of cat (attached image)
-Checked exhaust back pressure before cat vs after cat
-Cooling system temp sensor
-Plug wires
-Spark plugs
-Air filter
-Fuel pump/filter
-Fuel pressure checked on fuel rail
-Cylinder pressure checked (slightly lower on cylinder 8 but still above spec)
-Cleaned and inspected fuel injectors
-Changed trans fluid/filter multiple times
-Replaced all solenoids, governor or whatever else on valve body and accumulator spring (which was of course broken)
-Pulled valve body, cleaned and checked all valves, upgraded tcc lock plate with bigger orifice
-Upgraded Trans Cooler
-Adjusted TV cable
-Engine oil/filter multiple times
-Flushed radiator multiple times
-Idler Pulley
-Water pump, fan clutch, thermostat
-A/C flush and repair
-Trans cooler line check valve was taken off
-ECU/PCM was replaced (unknown reason by someone else)

Known issues are only a small leak from connection at muffler after cat and small engine knock at idle.
Plan to try other spark plugs and replace upstream o2 sensor plus anything anyone could recommend!

Attached image is borescope view on catalytic, looked very clean and the same from each end inside


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