First of all, welcome, there is a lot of wisdom here! You may want to repost the question in the Jag forum as this part of the board is mostly for introductions.
That said, I suspect the issue is the 6 or 12 cylinders firing. I had a Mazda 6 with a V6 - drove it on a very very damp day with not all the cylinders firing. raw and partly combusted Gas was therefore washing down the cylinder walls and into the exhaust. Got to my destination, cat was red hot - and I had ruined the engine.