24# injectors with a stock 4.0 map sensor will run like crap. Now, with a map adjuster set for 4 volts it will run like a champ and get improved mpg's.
On a stock 4.0 at 5200 rpm's your slugs are moving at about 3k feet per sec.
For a stroker 4600 rpm's is at the 3k mark. Sure you can go higher, but with a cast rotating assembly anything after that for sustained periods is sure to bring an early grave.
The switch you pulled sounds like the 4wd light indicator switch. The speed sensor is inline with the speedometer cable behind the gauge cluster. Does the torque converter lock up? There is a white colored plastic switch that needs to be depressed when the brake pedal is up.
The fan should come on at about the 215-220 range on the newer XJ's. The computer uses a thermistor threaded into the thermostat housing, however with age that sensors resolution may become diminished resulting in the computer thinking the engine is colder than it really is.
Sounds like the torque converter clutch isn't locking up, when the converter is unlocked it's going to make the most heat. You should get an external trans cooler if you don't already have one.