99 Ram 360 no power. I\'m at a loss why

First, I have a 99 Ram 1500, 5.9 gas, automatic.
No codes, no misses, lots of intake noises, Just no power
Transmission shifts nice and firm
50 psi fuel pressure, even when driving.
Back pressure is no more than 4psi, even though the rear o2 sensor has the same pattern as the front one in live data.
I’ve disconnected the evap line and ran it, no change. (Throttle port plugged)
I ran it with the pcv valve disconnected. (Intake port plugged)
I had the transmission shop look it over and check for codes, nada.
This started all of a sudden like one morning.
I’ve replaced the plenum, but it wasn’t even blown.
Replaced the coil
Replaced front o2 sensor

I’m not sure what else it could be. It runs good, just without any real low end power. This thing use to kick you like a mule when it took off. Now it’d be lucky to turn the tires over in the mud.