Jaguar is working on a track-focused XKR-S with increased power and design modifications over the standard version.Our spies spotted the new model undergoing circuit testing. The British automaker hopes to pit its new supercar against the likes of Porsche’s 911 GT3 RS and Audi’s R8 GT.The new model retains its supercharged 5-litre V8 powerplant though rumour has it power will be increased from to 410kW to 447kW.LIMITED RUNJaguar has added a host of modifications to the new model in line with its track-derived underpinnings. In our spy images you can see design changes to the front bumper, a tweaked bonnet with more air intakes (again hinting at a more powerful engine). You can also spot massive racing brakes and a racing wing at the rear. Further evidence of the vehicle’s track-focused nature is the lack of rear seating and roll cage fitted in the cabin. The new model could make its debut later in 2012 though, since Jaguar will only be selling 100 units of its XKR-S, it’s likely only a handful of this track toy will be offered.