1991 B series 2.6Lt petrol engine 'Heat' indication on dash.

This indicator has just appeared on the dash.
Is it something to do with the catalyptic converter (I hope I spelt that right). I was having problems with rough power under heavy acceleration so I replaced all the plugs and then this indicator appeared. It seems to have no bearing on the quality of engine power. Can anybody help. TIA

What indicator is it?

is it on constant or only after running for a lil while? and can you take a picture of the light?

The light is on full time and yes I can take a photo of it. I will do that on Sunday and post it on Sunday night. I have been told that it is an indicator for some kind of converter mounted in the exhaust near the exit of the manifold. They appear to be fitted on imported vehicles due to clean air laws in the makers country (Japan). When they fail they can be replaced at extreme cost (about $NZ2000) or removed and replaced with a small muffler. So far that is all I have been told.

Thanks for all the help but I have had the converter removed this morning NZ Time and the indicator has gone out. He is the explanantion of what happens. When the converter plays up the sensor shorts out and the indicator comes on. At this point one of two things can happen either the cobverter is replaced with another converter or a small muffler. The job the muffler does is to reduce the amount of 'rumble' in the exhaust note.
The cost of a new converter is about $NZ2000 where as a new muffler was only $NZ165.00 fitted and only took an hour. So again thanks for all the help.