The long-awaited new Subaru Impreza WRX STI is finally here. We’ve already seen first pictures of the new STI, but we’ve had to wait until today for real details.Now, with the car’s official unveiling at Tokyo today, we can fill in the gaps.The STI gets a quite different look to the standard WRX, with blistered arches and a larger spoiler giving it a seriously purposeful look. At the rear is a diffuser, surrounded by four tailpipes.At 1795 mm wide, the new STI is 55 mm wider than the WRX, while front and rear tracks are 45 and 40mm wider.Wheels are 18x8.5in with 245/40R tyres; Subaru purists will be please to know that gold colouring is an option.Under the bonnet’s large air scoop is a thoroughly updated version of the old STIi’s 2.5-litre flat four turbocharged engine. The engine now produces 296bhp at 6000rpm (up 20bhp) and 300lb ft at 4000rpm (up 11lb ft). Subaru hasn’t released any performance figures yet, but expect the STI to at least match the old car’s 5.0sec 0-60mph and 158mph top speed.As before, power is transmitted through a six-speed box (revised for a slicker shift) to Subaru’s symmetrical all-wheel drive system, with a centre viscous coupling plus front and rear limited-slip-differentials. The centre diff can be controlled via a switch in the centre console, called DCCD for Driver’s Control Centre Differential. This allows manual selection of torque distribution front to rear, ideal for anyone who enjoys powersliding. It also has three ‘auto’ modes.New to the Impreza is Subaru’s Si-Drive system, as used in the Legacy 3.0R Spec B. This gives the driver three different engine-response programmes at the turn of an iDrive-like dial, from standard to Sport to ‘Super-Sharp’. For the first time on an STI, there is also switchable traction control, and electronic brake force distribution for the Brembo brakes.Subaru reckons the cabin is posher than ever. Leather and Alcantara seats are standard, with Recaro sports seats an option. The new STI goes on sale in the UK in March, when it’s expected to cost around £28,000.