Thanks to a cunningly re-programmed ECU, high-flow catalyst and sports exhaust silencer, the Prodrive-boosted STi now develops 300bhp at 6000rpm, with a walloping 299lb ft of torque at 4000rpm. Big improvements over the standard car's 262bhp and 253lb ft, I think you'll agree. Best of all, these gains don't come at the expense of flexibility, for the new peak outputs arrive at exactly the same revs as in the standard STi.

You don't need to be Einstein to work out how these figures translate on the road. It's the torque you notice first. Big and beefy from 3000rpm, the PPP-STi has muscle to flex where the standard car flounders. Floor the throttle in third gear from 20mph and the acceleration gradually, insistently squeezes you back into your seat, gently at first, then building rapidly until all 299lb ft are compressing you into the cushion.

That's just for starters, for it's the transition from brawny torque to fizzing top-end power that's the really satisfying, addictively violent sensation. The stock STi, though quick, has always felt like it's straining against an invisible leash above 6000rpm. The PPP STi fires you like a steam catapult all the way to the rev limiter. It feels smoother too, singing more sweetly, responding cleanly and with more precision than the cooking motor.

You don't need a stopwatch to know it is significantly quicker. If anything, the sensations you get from behind the wheel suggest a bigger improvement than the claimed figures, although as you can see, these take no prisoners. According to Subaru, the uprated STi hits 60mph from a standstill in an eye-watering 4.6sec, compared with 5.2sec as standard, while the 0-100mph time drops from 13.7 to 12.2sec. Top speed is now a mighty, but largely irrelevant 155mph.

But as fans of the old Impreza Turbo know, it's in-gear response that counts, and that's where the standard STi has always struggled, thanks to a significant void in the power and torque curves. Basically, unless you've got 4000rpm showing you need to change down a gear to get meaningful acceleration. Not much of a chore on a B-road but a bit frustrating on the motorway.

Sit at 50mph in fifth in the standard car and it'll take you 6.1sec to reach 70mph. In the uprated STi, you'll get there in just 4.9sec. Likewise the 80-100mph increment in 6th, which takes the standard car 7.8sec compared with 6.5sec in the PPP car. Basically, whatever gear you're in, whatever the revs and whatever speed you're travelling at, the uprated car is significantly faster.

Prodrive offers a huge range of other upgrades, including bigger wheels and tyres, larger brakes and lowered, stiffer suspension; the car we tested was stock apart from the Performance Package. Despite the major leap in performance, the chassis copes well. If anything it feels better for having more to deal with. Now, rather than wrestling with scrabbly understeer then snap oversteer as the front differential fights to keep control then gives in and sends a big dollop of energy to the rear, the more potent PPP car simply settles into a mild and more easily balanced oversteer stance.

It's still a very different experience to that of an Evo VII, thanks to the Impreza's weightier, less nervous turn-in and more steadfast tail. That said the STi is a more natural handler and more predictable on the limit than the at-times-wayward Mitsu. It might lack the aggression and extreme adjustability of the Evo but it's still mighty effective. Now, with the added grunt and urgency it has the straight-line pace to compete on equal terms.

At ΂£1995, including fitting, the PPP upgrade provides a serious increase in performance for a reasonable investment. There's also the reassurance of knowing that Prodrive had to ensure the upgrades didn't compromise reliability, as the PPP is still covered by Subaru's full three-year/ 60,000-mile warranty. Of course there's always the temptation to go that little bit further and splash out on the Prodrive chassis upgrades as well, but as the wheels, brakes and suspension options are available separately you can always buy them in stages. However far you choose to go, a PPP-equipped STi is the Evo VII's stiffest opposition yet.