At its launch in 2009 Lexus confirmed that its V10 LFA supercar would be limited to 500 units in total and that the model would be painstakingly assembled at the rate of only 20 per month.At that rate, production of the LFA was forecast to end in December 2012. While Lexus has never mentioned any other versions of its LFA beyond the standard and track-focused Nürburgring edition, it would be a shame to not give one of the Japanese automaker’s greatest supercar achievements a proper send-off.PROPER SEND OFFThat farewell may arrive in the form of an extreme “Final Edition” model. A mysterious Lexus LFA prototype was spotted racing around the Nürburgring circuit in Germany. At first glance is sports all the styling changes as the Nürburgring Edition. Closer inspection reveals new elements which suggests this could be an even wilder version of the supercar.Image gallery!Apart from the new blue paint job, the prototype has an additional air intake on its bonnet, a subtle boot-lid spoiler and four exhaust tips instead of the regular three-pipe, triangular design. In fact, the exhausts have been moved to just below the tail lights to make way for an aggressive diffuser integrated with the rear bumper. In our spy images you can spot the letters “AD-A” plastered on the prototype’s flanks and both its bonnet and roof have been left unpainted.Given the modifications to the exhausts, we suspect there is a revised engine under the hood, one that’s almost certain to produce more power than the 411kW 4.8 V10 found in the standard LFA. The six-speed sequential transmission will likely have been reprogrammed for quicker shifts.If Lexus improves the suspension and we could be looking at a LFA capable of lapping Germany’s premier racetrack even quicker than the 7min14.64 set by the Nürburgring Edition.In 2011 rumours emerged that Lexus was planning a new special edition of the LFA that would feature an unpainted roof. The supercar, dubbed the “Tokyo Edition" due to its expected reveal at the 2011 Tokyo auto show, was a no-show but this new model could be it.Toyota Motorsport GmbH says this wild LFA prototype is not one of its projects.