Just stumbled across this video this afternoon and I thought it would be of interest to others here.
Unfortunately there is no information about the mods to the car but in the last half of the video you can hear the sweet song of the supercharged engine at full chat on the dyno.
BTW, this is NOT a standard XJR car. This seems to be a heavily modified track vehicle.

 

Clearly a lot of money was spent here, I’d keep it a secret too

 

It is a inline 6 engine , can't tell if its a X300 by a sagging headliner though

Looks like a lateral brace on the back of the engine

Notice the left door side mirror

 

I would guess it is going to be raced on JEC saloon & GT series or similar (like the swallows jaguar prepped xjrs) so I understand why they are not going to publish too much info

[Edit] downloading the video and zooming seems like the plenum has Swallows racing logo on it

 

Crossposting this here as I did not want to create new thread and i could not think of better thread

Twincharged AJ16

 

In the description on Youtube it says it's the Swallows team car. Here is that car at Castle Combe in 2018: