Cant be sure that it could be a legitimate issue, coz like in the key "ON" position, the light shows up, even before starting the car. And the other matter is no catalytical converter, running a test pipe with straight-thru setup
And about the cluster, ya maybe this light could mean something else on the original cluster. Or maybe the Cat Temp Light was always on after de-catting and previous owner made sure bulb wasn't working, like it works only when positioned properly. It never turned up before I worked on the cluster. Don't have a friend with an EG, should look around a bit.
Could remove the bulb, rather than messing with the circuit