For some performance junkies not even the 410kW and 800Nm of the latest Mercedes-Benz CLS63 AMG with the optional AMG performance package is enough to scratch the itch.
For these very special people, German tuning haus MKB offers an upgrade programme for Affalterbach's finest that boosts the output of the original 5.5-litre biturbo V8 to 515kW and a tar-wrinkling 1000Nm - which, as we know from previous AMG efforts, is about as much as a Mercedes-Benz rear axle can handle.
MKB claim their CLS63 is good for more than 340kmh, given a long enough test straight.
The result is impressive - or scary, depending on whether you are driving the MKB or the car that it has just showered with rubber shavings.
LIMITED TO 300KM/H
This luxury four-door coupé disposes of the 0-100km/h sprint in 4.1 seconds (two tenths quicker than the standard car, even with the AMG performance package) and is electronically limited to 300km/h.
But wait, as they say in the infomercials, there's more. When fitted with special high-speed tyres (which we strongly suspect may not be street-legal) MKB will re-programme the CLS's ECU without the limiter - at which point they claim it is good for more than 340km/h, given a long enough test straight.
Apart from a set of very special alloys, the MKB-tweaked CLS63 looks very standard from the outside, making it arguably the most outrageous street sleeper we've yet seen.