The range-topping Subaru BRZ STI has been teased via pictures on the Japanese manufacturer’s website. A higher performance variant of the rear-wheel drive BRZ coupe – which is twinned with the Toyota GT86 – has been rumoured for some time, thanks to the regular car’s naturally aspirated engine, which differs from Subaru’s typical turbocharging policy for its performance Impreza WRX.

Whether the STI features a turbo or a supercharger is currently unknown, but its 197bhp, 151lb ft 2-litre flat-four engine isn’t likely to have much more performance in it without forced induction. 250bhp is a likely target for a BRZ STI, moving it much closer to Nissan 370Z and Porsche Cayman territory and helping it keep up with the turbocharged hot hatches which currently beat it on price.

While the standard BRZ hits a 140mph top speed and completes 0-60 in 7.5sec, a car with forced induction would easily top 150mph and hit the 60mph benchmark around a second quicker thanks to its extra torque. Acceleration and general mid-range performance should feel a big step on from the standard car, too. An STI is unlikely to get an automatic transmission, its only gearbox option set to be a six-speed manual.

Another big change likely for a BRZ STI is an improvement in tyres. The standard car wraps its 17in alloy wheels in eco-minded skinny Michelin Primacy Tyres, the STI is almost certain to upgrade to 18in rims with stickier, more performance-minded rubber. The Toyota GT86 TRD, despite boasting no more power than standard, uses Yokohama Advan Sport tyres.

Styling wise, expect the BRZ STI to resemble the identically named concept in the pictures above. It appeared in late 2011 sporting Subaru’s famed World Rally Blue paint, a huge black spoiler, quad exhausts and big multispoke alloy wheels.

The BRZ STI looks set to appear later in 2013, perhaps at November’s Tokyo motor show to reflect Subaru’s home market. Expect its price to start at around £30,000, up on the standard BRZ's £24,995 tag.