It seems that today even highly exclusive track-only supercars have teaser campaigns, so the car unveiled at Pebble Beach isn't the final vehicle, but a production preview of the real deal.
We know from before that the P1's hybrid drivetrain, with a 3.8-litre twin-turbo V8 at its heart, will have its power output increased to 736kW (1000 metric horsepower). That's up significantly from the 673kW/900Nm developed by the road-going P1.
The GTR has a fixed ride height and rolls on slick racing tyres from Pirelli, which are mounted on 19-inch lightweight alloy wheels with centre-locking nuts. An on-board air jacking system allows for quick tyre changes.
Surrounding the updated drivetrain is a reworked body that's been pumped up and massaged for maximum aerodynamic assistance. At the front, the P1 GTR features flared wheel arches to house the car's wider front track (up 80mm), as well as a more aggressive front splitter, revised ducts for the low temperature radiators and an aero blade behind the front wheels to help "clean" the surrounding air.
A snorkel air intake, similar to the one present on the McLaren F1, sits on the roof, while along the sides the P1 GTR features repositioned wing mirrors and reworked ducts that funnel more air to the car's high temperature radiators.
The rear is dominated by a wing that sits on carbon fibre pylons that extend out from the back of the GTR. Unlike the road-going P1, the GTR's rear wing has a fixed height, but it does feature a hydraulic drag reduction system.
As we revealed earlier, the P1 GTR will housed, maintained and prepped by McLaren, with each "owner" entitled to a personalised programme involving company organised race days, as well as access to experts and facilities usually reserved for McLaren's racing outfit. The GTR programme will cost around 1.98 million pounds ($3.6 million) and will only be offered to owners of the road-legal P1.
The P1 GTR won't enter production until the final road-going version finishes winding and wending its way down McLaren's production line. This is likely to occur around the middle of 2015.