I'm finding it hard to refrain from describing this car as a Subaru Impreza, which is something I really shouldn't do even though that's basically what it is. The background to one of the most confusing opening sentences I've ever written (and there have been many of those over the years) is that Subaru, in its attempt to consign its sporting image to the history books, has decided to reserve the Impreza name for diesel and non-turbo petrol cars, of which this is neither.To confuse the matter slightly, the hottest Subaru in existence - the Cosworth STI CS400 - is still called an Impreza, but that's only because it has been selling slowly since it was launched in the pre-name change era and is still on sale. The WRX STI, a more current model, doesn't get to use the I-word.Perhaps by way of compensation, it's also the only Subaru available in the UK both as a five-door hatch and, as here, a four-door saloon. The Impreza hatchback is not an especially pretty car, and it becomes less so the more you add styling and aerodynamic bits and bobs to it. For me, the saloon styling, while still not what you might call elegant, is an improvement.The boot raises the WRX STI's standard luggage capacity from 301 litres to 420 litres, though of course it doesn't have the option of foldable rear seats which give the hatch a potential 1216 litres of space.Apart from that, Subaru quotes almost no changes at all. At the time of writing, the price is £32,995 no matter which body style you choose, and the 296bhp two-litre turbo petrol engine gives a 0-62mph time of 5.2 seconds, combined fuel consumption of 26.9mpg and CO2 emissions of 243g/km.The only difference is that the cleaner rear-end aerodynamics of the saloon allow for an increase in top speed from 155mph to 158mph, though I suspect that in the real world, rather than the world of official figures, the saloon might also be fractionally faster on a track day and perhaps a shade more economical on the road for the same reason.I'm also inclined to think that the saloon should weigh more than the hatch, since there's more of it. According to the figures in front of me, though, it doesn't.The performance figures mentioned above will already have conveyed to you that the WRX STI is very quick. In a straight line it wouldn't see the Cosworth for dust, of course, which is partly why the Cosworth is £18,000 more expensive. More surprisingly, the STI seems less comfortable with 296bhp than the Cosworth does with nearly 400.If you've never driven anything like this car, its handling will seem almost supernatural, but compared with several hot Imprezas of the past it's not quite right. At its best, Subaru has been able to conjure up a magnificent balance of relatively soft springing and excellently judged damping for its performance cars. When it doesn't quite do this, the result is disappointing to long-standing Subaru fans like myself, and I'm afraid the WRX STI goes down in my book as one of the lesser models of its type.The soft springing is there, and of course so too is the division of the engine's considerable power among all four wheels. Fine so far. The problem is that the damping, particularly at the front, isn't what it might be, so there are occasional moments in mid-corner or on mid-crest when the nose seems uncertain of where to go next. Moderately good Imprezas have sometimes been like this. Great ones, never.Despite the suspension set-up, the ride is quite harsh thanks to the unforgiving nature of the tyres. In fact, the WRX STI is less comfortable over less than ideally surfaced roads than the Cosworth, which I must say came as a surprise.As fast saloon cars go, this one isn't bad, but it's not a patch on the great Imprezas of former years. Given Subaru's determination to distance itself from its sporting heritage, that may be quite apt, though personally I'd prefer it if the tradition had ended on a higher note. Engine 2457 cc, 4 cylinders Power 300 bhp @6000 rpm Torque 300 ib/ft @4000 rpm Transmission 6 speed manual Fuel/CO2 26.9 mpg / 243 g/km Acceleration 0-62mph: 5.2sec Top speed 158 mph Price From £31551.00 approx Release date 01/09/2010