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I can't seem to find out why my exhaust system is getting really hot I know the exhaust gets hot but this exhaust is getting so hot that you can't even put your hand near the tail pipe or it will burn your hand. I've changed all 02 sensors, both cats, new spark plugs and changed thermostat. truck has no check engine light and is giving no codes. What the hell is going on?
I fully understand alloro's logic here. But I will make a noticable suggestion.
I had a similar problem on my '92 302. All new exhaust, cat, muffler, O2, plugs, wires. It finally ended up being the truck was running to lean. The PCV valve was a parts house "Cheapy" and wouldn't meter the correct flow of air from the valve cover. It just stayed open! Would only throw a code now and then. And speaking of hot enough to burn your hand, I was having the problem in winter. When I removed my gloves and ran the back of my hand across the tailpipe, it cinged and frayed all the hairs there.
When you did all the mentioned work, did you unhook the battery cable and give it a chance to clear the KAM? It may need to relearn with new sensors installed, since it may just be using the prior strategies to run before you did all this work. Also, be sure there isn't a bad hose from the rear PCV valve to TB and that all VAC lines are in good condition. This may be a good time to replace all vac lines.
I did consider a possible lean condition, but since there are leaps and bounds of technology (OBD-II vs. OBD-I) since say your 92, a lean condition severe enough to raise the exhaust temperature would throw a trouble code.
I would say that yes, leaps and bounds versus the 'ol OBD-I. I don't know for sure if burn your hand is an accurate temp, though I wanted to throw that out about how bad mine was.