A video’s turned up of what looks and sounds like an FXX/LaFerrari derivative running a Turbo Charged engine, possibly the F1 power unit or close relative of it.
The car as you can see has a snorkel on the top, which is a strange addition to the Ferrari cars it looks like it’s a member of. It would make sense for Ferrari to get some running on the engine, as it’s well ‘understood’ that they are struggling with their power train, especially on fuel usage.
There is also theories that the car may well be Ferrari’s return to LMP1 racing, and using the Power train from the F1 car would then be a good idea. Cross development would help both cars, and allow Ferrari to legitimately do more testing on the hybrid system.
Only time will tell if the car is a one off, or a serious return to LeMans