It was reported on pickuptruck.com, that insiders that work at Toyota have seen/heard that Toyota is producing amazing numbers out of a 5.7-Liter V8 Supercharger.

Do we need a Toyota tundra that fast?

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...TRD folks revealed a new Toyota Sequoia equipped with TRD's long anticipated supercharger bolted on its 5.7-liter iForce V8 - the same eight cylinder engine shared with the Tundra - sitting outside in the parking lot… TRD claims it's rated at 504-horsepower. That's 123-horsepower more than the naturally aspirated 5.7-liter V8. No word on torque.

... pictures of what looks to be a legit TRD compressor on top of a 5.7-liter V8. And Toyota has previously stated its 5.7-liter TRD supercharger was rated at "around 500-hp" on its project trucks, like last year's Toyota Tundra Double Cab TRD Off-Road Concept.

... sources at Toyota have told us the 5.7-liter supercharged Tundra has been clocked running the 1/4-mile in the mid-13s. They also say it will be the fastest vehicle in the Toyota lineup, excluding Lexus and, ahem, Scion.