Overheating Cats (cats only, not engine)

[Venom SHO s7]

Anyone ever experienced over heating cats during normal driving? It can idle all day fine, but under load, the cats get cherry hot after just a short trip, then the car boggs really bad, tach starts acting up a bit, and engine can barely free rev. After the cats cool down, its drives okay again.
Car has new plugs and wires, intake and valve cover gaskets, cats are good (my other SHO passed emissions with that same y pipe, and i just intalled that y pipe because i first thought the old cats were the ones that were clogged).
Also, it passed emissions fine just the night before it started doing this.

 

[wood_e]

Your car is running rich probably. Check your engine codes to see f you have any stored ones. I would also replace your ECT

 

[luckyGAT]

A friend of mine had a problem like that with his supra .Ill ask him what he did to fix it and let you know.FYI he was also running a tiny bit rich.

 

[Venom SHO s7]

Ill try the ECT, it mightve gone downhill after the emissions somehow.

Yeah, if you find out what he did, let me know.

Thanks for the suggestions so far.

 

[projectSHO89]

A faulty thermostat that keeps the engine from reaching operating temperature can also keep the mixture rich leading to glowing cats.

Steve