That this is a hell of a stock motor. Renntech dyno'd the A45 AMG at 340.6 to all four wheels. This is on a all wheel drive SuperFlow dyno which corrected the wheel readout to 389.5 crank horsepower or let's just call it an even 390. For an all wheel drive dual clutch car to exceed its quoted output is very impressive and shows the nature of the horsepower war going on right now which is about delivering more than quoted output. Speak softly and carry a big stick if you will.
For those not familiar with the SuperFlow dyno it is inertia based like a Dynojet but it has an internal eddy current based braking system. Depending on what mode is used, say pure inertia with no braking, it tends to read a little bit higher than the Dynojet. That is likely what mode was used here as it would be unlikely for this motor to put out even more power on a Dynojet as this is already huge output. Expect ~10% less so roughly in the 31X all wheel horsepower range on a Dynojet which correlates well with the internally calculated 389.5 crank horsepower figure. That's 24 horses less than BMW E92 M3 V8 level of power.... from a 2.0 liter four cylinder no less that is sending power to all four wheels.
The question now is how much is left in the motor for tuners? Mercedes pushed this one pretty far for a stock motor and that's impressive. This is going to be a fun motor. Huge thank you to Renntech for the dyno!