Dodge Ram 1500 Extended cab Long bed 5.9l 46Re
I've owned this Ram for about 3 months now. The previous owner attempted to fix the truck up and ended up letting it sit and I'm going and replacing everything that's cause for concern. I have replaced the 46re with a rebuilt and the TC. New water pump,thermostat, and thermostat sensor that runs to the PCM.
We had to cut the muffler from the baffles being eating away from rust.
After we cut the muffler I ran smooth as butter exhaust wasn't too loud, and no issues with cooling or slugging.
As of 2 weeks ago my engine went into limp mode and wouldn't go above 30mph. Bad Coolant Temp Sensor plug(Fixed).
I have no issues with speed just as my RPMs go up the engine gets dragged down with the load % only being about 3-11%. The exhaust starts are violent vibration noise but only after the engine warms up.
I've seen on the forums that people have had issues with the Cats Falling apart inside and causing issues; which leads me to believe that my cat is clogged or the baffles are busted and as it heats up it starts restricting.
Fuel Sys 1 - (CL)
Fuel sys 2 - (N/A)
Calc load - (3.9%)
STFT B1 - (-0.8
LTFT B1 - (14.8)
Map - (10inHg)
RPMS- (705)
Speed - (0)
IAT - (160F)
o2s B1S1 - (0.880V)
STFT B1S1 - (-3.1%)
o2s B1S2 - (0.740v)
STFT B1S2 - (99.2%)

 

If your exhaust flow is low after things warm up, it's quite possible that you cat may be restrictive and needs to be replaced. If it's original, it is 27 years old and nothing lasts forever.

Just FYI, I replaced my cat several years ago with a Magnaflow Converter - 99047HM (dual 2" inlets, 3" outlet, front O2 sensor port) so that I could easily run 3" exhaust from the cat back. Also, installed a Dynomax UltraFlo Welded Muffler - 17233 and a straight length of 3" exhaust pipe (with a welded on O2 bung for the downstream O2 sensor and a 3" tail pipe.

 

There was recall on pre 97 cat's, They broke and would rattle. I also replaced mine(1996) with the Magnalflow cat(direct replacement). When i cut open my original cat it was broken in half with small pieces on the bottom.
I would put the cat and the plenum gasket on that list.