Designed to be a bolt-on, the ASA supercharger runs at relatively low boost. On the other hand, more power can be produced with a higher boost-provided the owner can shoulder the expense of rebuilding an engine with low-compression pistons and strengthened internal components.

With boost set at 8.7 psi, the ASA supercharger adds 149 hp. The total head count rises to 545 hp at 6800 rpm, accompanied by a healthy 435 lb-ft of torque at 4600 rpm. This extra power helps launch the car with the determination to reach 62 mph in 5.5 seconds, a full half-second faster than stock.

The subtle link between art and brute force is illustrated perfectly by the Maser's supercharged V8. In naturally aspirated form, its power delivery is a thing of beauty in the way it feeds layers of sound and sensation as it moves rapidly from idle to its 7500-rpm redline. One of the ASA supercharger's strengths is that it doesn't alter the engine's character, just amplifies its power and torque.

In normal driving, it's the beefier torque curve that makes the real difference to the way the car is driven. The motor doesn't need to be revved as hard to achieve the same speed; full throttle now delivers a solid push in the back rather than just a consistent buildup of speed. This extra rush turns a good engine into a great one.

The car's one serious weakness is the jerky Duo Select manu-matic transmission, which many view as an inappropriate gearbox for a luxury saloon (a proper, torque converter-equipped ZF six-speed automatic is now available as an option and has enjoyed a warm reception, especially in the U.S.). Even so, with a partial lift of the throttle when upshifting, it's possible to smooth out the gearchanges.

Nor are the brakes perfect. They don't seem to really bite and scrub off speed in the manner expected from a high-spec Brembo system (this car is based on a '06 Quattroporte Sport GT; the Sport GTS launched at the end of 2007 uses iron/aluminium brake discs for greater fade resistance).

The suspension is also standard, with only the 8.5- and 10.5-width 20-inch AEZ forged alloys, and 245/35 and 285/30 Dunlop SP Sport Maxx tires making the difference. While this combination lowers unsprung weight slightly over the factory 20s and the larger rears provide more grip, the 151 extra horses are still more than enough to bring the chassis to the end of its tether. Coupled to the weak brakes, this holds the car back from realizing its full potential. Pietz was aware of this and wanted to upgrade the chassis to match, but the dealer didn't see the need; he's not a hard driver.

He soon changed his mind, though, when his good friend-a Mr. Michael Schumacher-drove the car and remarked that the engine was brilliant, but the suspension and brakes weren't up to scratch. Thus enlightened by the master himself, the dealer has now seen the error of his ways.

There is no question that, from an aesthetic point of view, the Maserati Quattroporte is the most interesting car in its class, certainly the individualists' choice. Where the Quattroporte's out-of-the-box performance is only fair to middling when compared to its peers, the TTP supercharger conversion gives it the edge it needs to stay in touch with more powerful rivals. When the suspension and brakes are also sorted, this is one competition the TTP-tuned Maserati will be able to call a level playing field.

TTP Quattroporte Scuderia XL

LayoutLongitudinal front engine, rear-wheel drive

Engine4.3-liter V8, dohc, 32-valve, supercharged and intercooled, sport exhaust and catalysts

TransmissionSix-speed Duo-Select manu-matic

Wheels and TiresAEZ forged alloys, 8.5x20 (f), 10.5x20 (r)245/35 (f), 285/30 (r)

PerformancePeak Power: 545 hp @ 6800 rpmPeak Torque: 435 lb-ft @ 4460 rpm0-60 mph: 5.4 sec.Top Speed: 172 mph

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