The new model is based on the regular Impreza STI, but Cosworth has tuned the engine to produce 395bhp – almost 100bhp more than the standard car's 296bhp. That's enough to drop the 0-62mph time by a second and a half to just 3.7 seconds.
The car will have bespoke brakes developed by AP Racing, which supplies several teams in Formula One and the World Rally Championship.
At the same time, the suspension and exhaust have also been upgraded, as have the car's looks inside and out.
Production of the car is limited to just 75 units, and full details of the price and technical specification will be confirmed nearer the on-sale date.