The letters ‘STI’ hold a special sort of appeal for many Subaru Impreza enthusiasts. Think of ‘Subaru Technica International’ as the go-faster wing of Subaru much as M is to BMW, AMG is to Mercedes or, more accurately, Ralliart is to Mitsubishi. STI-badged Imprezas command serious respect and the officially imported UK cars are always in big demand.

It's fair to say that October 2000 was a significant month for Impreza owners. Out went the much-loved original shape car and in came the revised bug-eyed edition. The reception was frosty to say the least, as Subaru realised that the styling wasn't to the taste of hardcore fans and moved quickly with the launch of the Impreza UK300 which offered compound headlamps, bigger spoilers, and the option of a Prodrive WR kit that boosted power to 245bhp. The UK300 was an instant hit and Subaru UK subsequently introduced the Impreza STi at the 2001 Frankfurt show. Debuting in British showrooms in January 2002, the STI, a car that was launched with 261bhp and the option of a standard car or one with bigger Prodrive-designed spoilers, grille, and front bumper. Both were badged 'Type-UK' to differentiate them from parallel imported models.

The 2002 Paris Motor Show saw the release of the facelifted Impreza with much of the credit going to Prodrive and the designer of the McLaren F1, Peter Stevens. With revised front wings, shapelier headlights, a more aggressive bumper and front grille, a re-sculpted bonnet and revised rear light clusters, it was a far more cohesive design than its predecessor and sales soon picked up again, especially as its key rival, the Mitsubishi Lancer Evo VII, had just been toned down from its Evo VI heyday. Almost immediately Prodrive announced a performance pack for the STI offering a full 300bhp. A 2003 facelift saw the controversial bug-eye headlamps replaced and a raft of other changes brought in.

Introduced at the 2001 Frankfurt Show, the STI is powered by a 265bhp 2.0-litre flat four engine, but don't be fooled into thinking that it's merely a case of plugging in a more aggressive engine management chip or a bucket-sized turbocharger. The later 2003 facelifted car followed the same theme with revised suspension and a few engine tweaks. Nearly 80% of the STI's all-alloy powerplant is unique. The piston head was reshaped to form tougher semi-closed-deck cylinder blocks. Screw-in conrods and forged pistons combine with shimless valve lifters, sodium-filled exhaust valves and hollow valve intakes. Every moving part is either stronger, lighter or both. This reduces inertia and gives the engine a manic free-revving feel that's missing from the standard WRX. A larger intercooler and air intake help keep things from meltdown, and a water spray has been fitted to the intercooler that is operated by the driver via a dash-mounted button. Serious stuff.

Differences to the regular WRX include special gold-coloured spoked alloy wheels, colour-keyed sill spoilers and an interior featuring blue suede-effect seats with STI logos and red stitching for the steering wheel, gear knob and handbrake lever. Also, inside - and sure to please enthusiasts - is a switch to spray the intercooler with water. Another device allows the driver to pre-set a warning buzzer and light to guard against over-revving the engine. On opening the bonnet, the engine compartment greets owners with a dramatic mixture of colours and detailing. The intake manifold, for example, is painted in red and the enlarged aluminium intercooler emblazoned with STI lettering. In addition, the STI Prodrive Style features a massive high-riding boot spoiler, newly designed sill spoilers and a deeper, squarer front bumper. The grille and badging resemble the WRC rally car. Interior enhancements over the standard STI include dark blue-coloured instruments with red needles. Four colours were available: WR Blue Mica, Blue Black Mica, Premium Silver Metallic and Pure White, the latter two being available to special order only.

The car presented here is a 2003 Subaru Impreza WRX-STI Type UK which has built on its very sound standard specification and been further enhanced for even more performance and fast driving acumen. The discerning older owner of this special car, a renowned figure in motoring circles, has improved this car with superb engineering carried out by proper specialists. Specification summary:

• Engine by Subaru specialists Zen Performance of Cambridgeshire, who systematically rebuilt the engine to 2.35-ltrs, costing £12,700 (see images for build spec)
• Litchfield twin-scroll VF37 turbo fitted at 37,766 miles for more road-friendly manners (430bhp) and cambelt, costing £3,600
• APS 3.5-inch race exhaust
• AP 6-pot callipers and discs
• EXE-TC Competition Suspension units
• Exedy Clutch Europe Ltd twin-plate clutch 6-speed
• Whiteline Performance roll bars
• 4-point harness seat belts
• HID headlight
• Carbon rally-spec wing mirrors

The car has had just two previous owners before our vendor, one of which is a friend of his, who like him also didn't use it in the winter. Consequently, the bodywork is in as good condition as the mechanicals. It's accompanied by a large history file, fully detailing the specification, servicing and the recorded mileage of just 39,247. The car is ideal for fast-road driving, hill-climbs or sprint events. Its engineering has been overseen by an owner who has lived and breathed motorsport for decades, selecting the best people and parts to create this car. The car’s abilities are supreme, very useable on road, but comes into its own when sprinting or hill-climbing, a proper machine and offering staggering performance for this level of guide price.