Mercedes engineers have their hands full as they are trying to perfect the new C-Class AMG lineup. Both the sedan and the wagon have recently been spotted driven on a public road not far from the Nürburgring.

The changes are there, but you will have to look hard to notice them. There is a new exhaust system, a different rear bumper and some front clip changes on both cars. Things are more interesting under the hood, however.

All AMG C-Class models will ship with the world’s most powerful turbocharged four-cylinder engine rated at 421 PS in the base spec. Opting for the top C63 spec adds an electric motor into the mix for a rumored combined output of 557 PS.