Previous generations of the Nissan GT-R were renowned for their unlimited tuning potential. Depending on your budget, it was possible to get up to 1,000 hp from the car's turbocharged 2.6-liter inline-six.

But with the all-new 2009 GT-R, Nissan seems to have bowed to pressure from the Japanese government to keep modified cars off the streets, making it clear to GT-R owners that any modifications would automatically void the car's warranty.

The list includes removal of the car's GPS-based speed limiter, which holds Japanese-spec cars to a laughable 112 mph. This can be defeated only when the nav system recognizes that the car is on an approved racetrack, and even then, you are obliged to get the car inspected after each track outing.

None of this, of course, has scared tuners away from trying to extract the maximum in performance from the GT-R. At the top of that heap is the Power House Amuse Phantom GT-R, arguably the fastest and most powerful modified GT-R in the world.

The man behind this car is Hideki Tanabe, president of Power House Amuse. His workshop near Tokyo has managed to extract an additional 129 hp and an extra 138 lb-ft of torque from the stock twin-turbo 3.8-liter V6. The numbers speak for themselves: 602 hp at 6,500 rpm and 571 lb-ft of torque at 5,300 rpm, figures more commonly associated with prohibitively expensive exotica.

Starting with a Black Edition GT-R delivered last December, Tanabe transformed the car into something more akin to a club-sport version of the GT-R. Gone was the speed limiter, and engine management was retuned to work with substantially higher boost pressure. A full titanium exhaust replaced catalysts and bulky silencers. The added power provides explosive acceleration with every pull of the gear selector, sending the tachometer needle to redline in a split second.

The factory GT-R's Bilstein suspension system was modified with stiffer springs and threaded sleeves that allow for height adjustment at front and rear. The result is more precise steering thanks to the negative camber in the lowered suspension.

To help the driver hang on, Recaro carbon-Kevlar racing seats were added, along with a removable Momo steering wheel to ease egress. The seats and the lighter titanium exhaust shave curb weight by 100 pounds, to 3,690 pounds.

GT-R owners (at least those willing to risk warranty coverage) can find Amuse products in U.S. tuning shops.