Interesting. Does sound like they had to redo the exhaust for some reason in the past, but unless it is restricted (i.e. too small a diameter from the point the pipes merge), not sure why that would cause heat to build, without causing other performance issues due to too much back pressure in the exhaust.

I think at this point I've got no other ideas to help, but am still glad the aux fan made a difference.

 

I have a 2006 Silverado 1500 w/5.3L flex fuel. It came from the factory with 2 cats, 1 on each manifold. The 2 cats are part of a Y-pipe that goes to the passenger side. Then runs back as a single larger tube to a big muffler under the bed and out the side. So single exhaust with dual cats. The cats are fairly small and welded to the y-pipe so it acts as a single piece. It flows fine and is very quiet.
I have since done a cat back that replaces the piping and muffler starting behind where the y-pipe becomes a single tube. Bigger piping and free flow muffler. Louder but not obnoxious. Torque has improved quite a bit. Pulls much better off the line.
Stock and modified my coolant temps are always consistent.

I would venture to guess that if you have a plugged cat your engine temps are going to go up. Both oil and coolant temps. I've dealt with that with my 04 CTS-V having bad cats and running hot as hell. Replaced cats and all was good. It was also throwing codes because the O2 sensors upstream and downstream were not happy.

 

Good morning everyone. I pray all is well with you all. I'm returning today with good news to update the group with. I went and had new exhaust from the cats back put on my truck and boy what a difference did it make. Not only did it resolve the heating up issue, but it also seemed to have awaken the beast in my truck. It drives better, it has a more responsive throttle now, it gets a little better gas mileage and it definitely tows better. Thank you all for all of your advice and wisdom to lead me to my resolution. I wanted to drive it and take a few trips pulling my camper before I came back to update the group and so far so good. Again a big thanks to all of you.