A big front splitter and steeper spoiler should give this example more downforce.
Gallery: Tesla Model S Plaid Test Video
In front, this Model S wears a black splitter that juts out from below the fascia. Presumably, it works with the rear diffuser to balance downforce between the two ends.
In this video, it also appears that the clear rear spoiler has a steeper angle of attack than the piece on other pre-production examples. The element's design would make the job easy for the engineers to alter the slant and tweak the aerodynamics.
Judging from this car's shape, Tesla appears to have a high-downforce setting for the Model S here. Since the company can apparently remove or modify the splitter and spoiler, it's possible the company is evaluating the ideal amount of downforce for the Nürburgring's many curves without too much of a detriment on straight-line speed.
Rumours suggest that the Model S Plaid uses a three-motor powertrain making slightly in excess of 800 bhp and uses a 130-kilowatt-hour battery. Better thermal management could keep the cells running cooler by using a bigger refrigeration system.
It's not yet clear when Tesla intends to send the final version of the Model S Plaid around the Nürburgring and release a lap time for the hotter model. At this stage, there isn't much question about the vehicle lapping the Nordschleife quicker than the Porsche Taycan's 7:42, but there's still the mystery of how low Tesla can take the time.
Presumably, Tesla also intends to sell the Model S Plaid to the public, but we don't know when. Rumours suggest that it could be sometime in October or November of 2020. Although, Elon Musk later tweeted the timeframe could be as soon as next summer.