The ingredients are simple enough: take one 911 Turbo fitted with the factory 450bhp Performance Pack (consisting of bigger turbos and intercoolers), add a DMS-spec sports exhaust with freer-flowing cats and let electronics wizard Rob Young do the rest. The cost is ΂£4348 (΂£2233 for the re-map, ΂£2115 for the exhaust) and the results are simply stunning. DMS hasn't gone down the maximum-horsepower-at-all-costs route, instead concentrating on massive torque and smooth OE-style delivery. Even so, your investment gets you just over 550bhp and 530lb ft, gains of 100bhp and 117lb ft respectively.

DMS will also tune non-Performance Pack cars, but peak power falls slightly to around 520bhp. Over 80 Turbos have been through DMS's Andover workshop, and plenty of customers want even more power. DMS can deliver as much as 750bhp, but Rob usually persuades customers that 550bhp is more than enough. Any more and driveability suffers - the car actually starts to feel slower... well, until the big bang arrives.

There are no such inconveniences with the brand new DMS demonstrator. It does suffer from a shade more lag than a standard Turbo, much of which is down to those bigger turbos supplied as part of Porsche's own Performance Pack, but even cruising around with less than 3000rpm showing on the rev counter, the Turbo feels freakishly responsive. Wind the revs towards 4000rpm and the sports exhaust starts to sing and things begin to happen very quickly indeed.

Put simply, this tweaked 911 is one of the most ferocious cars I've ever driven. Inertia and weight are shrugged off as the mighty engine picks up the Turbo and throws it at the horizon with frightening force. The whole car seems to rear up as the acceleration builds, the nose pointing skyward ready for take-off. The way it pulls each successive gear with ever more venom is startling.

The standard 911 Turbo is a rapid car, perhaps the fastest point-to-point car, but with DMS's help it strides onto a performance plateau that puts it out of reach of all but the most exotic, expensive and impractical supercars. Apparently on Millbrook's mile straight it bludgeoned its way from zero to 150mph in 17.2 seconds. A Carrera GT would be less than two seconds quicker. Throw in narrow, bumpy roads and a good dose of British rain and Weissach's supercar wouldn't see which way this Turbo went.

Marrying this sort of pace to the standard Turbo chassis is not the mismatch you might expect. The Turbo absorbs every last trace of power and transmits it to the road so efficiently that it feels like it was designed for it. It drives like any other Turbo, from its informative steering and huge grip to its rear-biased handling balance. I imagine that in the wet you could get into trouble should you disengage PSM, but in the dry it feels very progressive. Even in second-gear corners it requires total commitment to get the tail really moving around rather than gently tightening your line, and as long as you stay on the power it's easily reined-in. I can't think of a car that would hang onto this Turbo's tailpipes for more than a couple of corners.

DMS has been very wise to build on the Turbo's strengths and avoid the usual stiffer springs, rock solid damping and bigger wheels that tuners feel compelled to fit. It has created a mesmerising supercar and its technical nous means that the remapped ECU is undetectable by Porsche diagnostic equipment, while the exhaust uses the OE tailpipes. By the way, the ECU upgrade alone takes the car up to 525bhp so you needn't go for the slightly louder exhaust if you want total stealth. It's the perfect crime.