That is a lot harder to say. The ECU controls the fuel in relation to the amount of air entering the engine measured by the air mass sensor. I would check the air filter is not blocked / restricted which could richen the mixture, but that is before the air mass sensor so it is a long shot. If it was mine I would take it to my Ducati dealer for investigation.
There have been a number of discussions on here about running temperatures. In general, the bikes tend to run cool at around 70 C, when on the open road but quickly get hotter in traffic. Ducati set the fans to come on at just over 100c to control the temperature and as long as they do, all is well. However, the low running temperature at open road speeds does tend to make people worry when the gauge starts to climb towards 100 and also, it is very possible, perhaps even likely that the ecu is providing a rich mixture at open road speeds and consequent low temperature. If this is the case with your bike, then that could be why your cat is getting so hot. It looks rather as though Ducati may be fitting thermostats that keep the coolant temperature below the optimum the ecu is looking for - not a problem in baking hot Italy but it is for us in our somewhat cooler climes. What is your typical open road temperature and how is your fuel consumption?
The basic fuel map is adjusted for temperature and the Lambda sensors should be leaning back the fuel air mix so a sensor problem is the most likely culprit but I would have thought that plugging it in and looking at the data should highlight any problem.
I don't suppose I could borrow it. A bike mechanic said to try and borrow one to see if it still glows
