Cadillac's CTS-V is even more powerful than even its builders realised.
The company originally announced that its high-performance saloon produced 542bhp from its 6.2-litre V8 petrol engine, but official testing has revealed that it has 556bhp.
The engine has also been certified as producing 551lb ft of pulling power and powers the car to a 0-60mph time of 3.9sec.
The CTS-V also has a specially tuned version of Cadillac's magnetic active suspension system and a new automatic gearbox with paddle-shift controls.
Cadillac has already claimed the production saloon lap record around the famed Nurburgring race circuit in Germany with the CTS-V, lapping the track in 7min 59.32sec.
The CTS-V is scheduled to go on sale in the UK early next year, although no prices have been released and speculation persists that it will be available as a left-hand-drive model only.