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
-IAC
-TPS
-MAP
-Cooling system temp sensor
-Distributor
-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

 

Did you check/reset the fuel sync after the plenum repairs? Your issue sounds like the timing is off, as that will make the engine sluggish as all getout. Lastly, has the timing chain and gear set ever been replaced with a new double roller timing chain and gear set?

 

I did not check or reset fuel sync after plenum replacement and will look into such, thanks. Oddly runs good otherwise at idle or on flat ground, plenty of pep. It's just when i have a bunch of weight in back and climbing up mountains at higher speeds.
As far as i know the timing chain or gears have never been touched.
I've read you can set the distributor with a multimeter since i don't have expensive scan tool but its not accurate enough? Any extra info about such would be great.

 

Speed density doesn't much care about vac leaks

 

Always wondered about map vs maf. Had to look up speed density, thanks for teaching me something new!

 

On a 2001 fuel sync is only used to start the engine, it has no bearing on ignition or injection timing. However double check that the PCM is correct for the truck as there are changes over the years. Maybe you're expecting too much, 1000+ lbs in the bed at elevation will certainly slow down the truck. One thing you could do is look at live data when climbing and look at fuel trims, O2 sensor and MAP readings. Maybe something sticks out.

 

It is highly possible im expecting too much, specially since it being a ram passenger van not truck so it does weigh more but i post here due to popularity since mechanical similarity of engine and transmission, nothing related to the shell. I just cant see anyone towing in this vehicle with such low power up mountains. Always have people towing passing by me when i just have about 500-600lbs inside. I've been holding off on building anything interior wise due to being scared by putting even more weight inside plus full load of water, clothes, food and everything else that quickly adds weight. At the most weight i had ever had was when i took my sister camping up at some arizona lakes, clocking in at 30mph OD off going up some inclines. I feel like a semi truck driver with hazards on up the mountain pass. Obviously high altitude also effects performance so i really could be expecting to much as you mentioned.
Going to replace a few more parts which would finalize everything as done except oil pressure sensor and a complete engine teardown and trans. I am still curious why they changed the ecu, old one was in the back of van when i bought it. I have read they are known to be buggy so I'll have to look more into that.
I appreciate everyone's input and the hundreds of posts on here I've gained knowledge from. All of you are amazing for taking your time to do so.

 

What rpm is the motor when you say it has no power? OD off.
What was it and did you test it under load(driving).
How come you didn't get the Hughes plate?
If you suspect the cat is clogged remove the front 02 and see if it runs any better.

 

There is no rpm tachometer in her (think it should be standard in all vehicles honestly). So i really have no clue what the tach is at any time but doesn't sound very high rpms while hill climbing with od off.
It seems to have a bit more power when its cooler but that's obviously normal and hard to come by in Arizona.

I removed up and downstream o2 sensors and stuck a boroscope camera down there to inspect cat. Looked super clean from what i saw.
Didn't have money at the time for Hughes upgraded plate plus don't drive it that often.
I did have my PCM fry out on a recent trip so that was fun and expensive tow (jdm pcm yay). Will be carrying spare pcm with me for now on. Also the new crankshaft position sensor i got (SKP) was rubbing a little. Definitely a good mm to 2 longer than oem.

I also have small evap leak code. Replaced gas cap and all the evap lines, reset pcm, still throws code but has unexpectedly turned off before.

I'm still not fully convinced its just that much of an underpowered engine though.
Is it possible to have no noticeable transmission problems but could cause something like low power? I have cooked the trans and engine a bit before but cylinder compression is fine and trans shifts okay. Slightly lower compression on cylinder 8 i think but was still in spec.