Re: erratic temp gauge..
Most likely the instrument panel. There'a a few places where the earth could be dodgy. A lot of XD-XF's do this. It starts very mild and then goes nuts!
1. Umbilical plugs which attach to the rear of the dash. Remove and cleans pins too.
2. Inside the instrument cluster, the fuel gauge itself attaches to a circuit board. Remove and clean connections.
393 Tremec TKO 9"