2018 Porsche 911 GT2 RS spotted testing at the Nürburgring

Is this a mule for the most extreme road-legal version of the 911? Our spies think so

We believe this development mule is the hotly anticipatedPorsche 911 GT2 RS, here seen testing at the Nürburgring.

The model, which looks set to become the most extreme production 911 ever sold, appears to be wearing a mixture of GT3 and GT3 RSbodywork and benefits from a larger rear wing and race-style winglets on the front bumper.

Aside from the extra aerodynamic addenda, the pair of enlarged rear intakes have our sources convinced that this car is running the most powerful flat six engine to make production in a Porsche.

The GT3 RS produces 493bhp from its naturally aspirated 4.0-litre flat six engine, but we expect the GT2 RS to offer close to 700bhp thanks to forced induction. It will be the hottest 911 model on sale.

Porsche’s latest limited-run 911 models, including the 911 R, have been based on the first-generation version of the 991. But this mule appears to be running second-generation rear lights, which backs up comments made last year by Porsche’s high performance boss, Andreas Preuninger, when he revealed that the GT2 RS would be based on the second-genration 991 and arrive at the end of the 911’s production life.

This points to a launch date for the GT2 RS some time late in 2018.

The last Porsche 911 GT2 RS to go on sale was based on the 997 model. It offered 611bhp from its twin-turbo flat six engine, in a package weighing just 1370kg. It is widely regarded as the most extreme 911 ever to go on general sale.