As marketing strategies go, this is one of the best. In the days of the first-generation Subaru Impreza, the fastest car you could buy through the UK dealer network was the Turbo. What the driving enthusiasts really wanted, though, were the more powerful grey imports like the WRX, the STi, the 555 and so on. Now that the new Impreza has arrived, Subaru is applying those names to the cars that it sells in this country, in the not unreasonable hope that they mean the same to Impreza fans as RS and Evo do to Ford and Mitsubishi folk.So the "ordinary" Turbo is now the WRX, and the new, high-performance version tested here is called the STi. As all Impreza-heads know, STi stands for Subaru Tecnica International, the company's motorsports division. What these people have done is to rework the two-litre engine so that it produces a shade over 260bhp while retaining reliability, road manners, emissions and noise levels that would be acceptable for a car which is meant to be used every day.Methods of achieving this include reinforced block and conrods, forged pistons, variable valve timing, a hefty clutch and a larger intercooler than that fitted to the WRX. You can manually cool the intercooler by operating a water spray button, but I doubt this has any real benefit other than to impress the guys in the pub.The brakes and suspension have been reworked to suit (the former supplied by Brembo), and the transmission gets a close-ratio six-speed gear cluster and Suretrac limited slip differentials at the front and rear. Wheels and tyres are subtly larger than those of the WRX - 7.5x17" instead of 7x17" in the case of the multispoke alloy wheels, while the tyres are just 10mm wider.So what is the effect of all this? Well, one of the first surprises is that the STi is astonishingly quiet. You're aware of the boxer engine's characteristic throbbing sound, but without having heard this car and a lesser Impreza side by side I wouldn't say the STi sounds noticeably different at low engine speeds (a different matter when you're pushing 7000rpm, of course).I've always reckoned that one of the keys to a good high-performance road car is its willingness to be driven very slowly, and the STi scores well here. You can potter around quite happily at 20mph if the need arises. The only slight problem is that in these circumstances a very small increase in throttle pressure can send the car bounding forwards. A marginally heavier pedal action, or at least a less sensitive one, would make town driving considerably easier.Other reviewers have said that the STi has very stiff suspension. I can't help wondering if they have been driving the same car that I was. Because of the low centre of gravity (due mostly to the flat-four layout of the engine), Subaru doesn't need to make its cars stiff in order to handle well. For a car of this type I think the STi is very soft indeed, which contributes both to phenomenal grip and to remarkably good ride quality. Even without considering those points, you only have to watch the bonnet rise as you start accelerating hard to realise that this is in no way a stiffly-sprung car.In fact there is so much body movement, particularly at the front end, that the STi has a definite tendency to understeer unless you do something about it. Again, there are contrary views about this. What most people seem to do, once they've worked up enough nerve to try it, is allow the understeer to happen, keep the throttle pedal buried in the carpet, and then wait for the action of the front diff to pull the nose back into line.This is all very dramatic, but compared to doing the job properly I think it comes a very poor second. If you wait until the car is settled in the corner and then start applying the power, the STi will rocket out on to the next straight in a very pleasing manner, with perhaps the gentlest twitch of the tail to remind you how hard it is working.At this point it might be worth mentioning that I didn't try any such tricks on the public road, but during a brief session round Knockhill racing circuit. I can happily say I have never driven a standard road car which could enter the notorious chicane quite so quickly and still come out pointing in the right direction (and at such speed that a change up to fourth gear was required while the car still had two wheels on the exit kerb). That impressed me far more than the screams emanating from the tortured front tyres of other cars which were on the track at the same time.On the road the STi is if anything more remarkable, since it combines excellent manners with performance that is greater than you could realistically hope to use unless you live somewhere with extremely long straights and no speed cameras or oncoming traffic.Its natural rival is of course the Mitsubishi Evo VII, and while CARkeys does not normally go in for comparisons (to say nothing of the fact that we have only so far driven Japanese-spec versions of the Evo) I'd have to say that the much greater suspension compliance of the Impreza makes it my preferred choice.Blue has become the classic colour for quick Imprezas, and the STi is available in two shades, or alternatively in silver or metallic as options only. You can also specify the Prodrive Style body kit, which looks terribly impressive - particularly the enormous rear wing - but does not add anything else to the performance. Prodrive Style cars are available only in the two shades of blue. Both versions share the standard Impreza package of a three-year/60,000 mile warranty plus six years' anti-corrosion cover, plus three-year membership of the Subaru Assistance home and roadside repair and recovery package.Second opinion: Almost perfection on the race track, the Subaru shows up its true colours on the road. This is a car for driving quickly, not pussy-footing about. The rally-bred suspension which makes it a delight to hussle round tight corners and fast curves is a positive pain in the bum at lower speeds. It's not as rock-hard as some, but a bit more give for everyday use would be appreciated. It's also a bit prone to understeer when not fully committed. This is a car for the enthusiast rather than the executive, but then again, you wouldn't be late for meetings! John Fife.