RacingSolutions took a brand new 2013 SRT Viper with the 8.4L V10 making 640 horsepower and bolted on their Twin Turbo system bumping up the power to 857 horsepower and 810 ft-lbs of torque at the rear wheels at 8 psi on a DynoJet. Accounting for driveline losses through the 6 speed manual transmission that puts this SRT Viper at 1,000 HP on 93 octane pump gas. They quote 1,100 horsepower when using E85 or race fuel.
This twin turbo package using Precision 62mm Turbochargers from RacingSolutions is a bolt on system requiring no internal modifications to the engine and is priced around $40,000.00. Higher end packages are available with additional power that include building the engine and driveline upgrades at around $80,000.00 Take a look at dyno data and video below.