Now, the M5 has an exhaust and even though it is just a rear section it does make a difference so keep that in mind. The C63 Black Series numbers look very high as an article posted on BenzBoost with several dyno runs from C63 AMG Black Series cars on a dynojet in SAE correction were nowhere near what was hit here on the EAS dynojet dyno. Once again, the EAS dyno shows that it reads a bit high.
The most glaring inconsistency though is the "claimed" E63 AMG Performance Package dyno run. This graph just does not look right based on all other runs as a reference point and the only explanation is that this graph was posted to make the BMW M5 look better on a certain BMW fansite. The car had to be heat soaked severely on purpose (most likely scenario) or not a Performance Package vehicle (or flashed with different software) and Bimmerboost does not like this kind of blatant and blind fanboy favoritism.
Here is a dyno comparison on a dynojet of a standard CLS63 AMG, a Performance Package CLS63 AMG, and a tuned CLS63 AMG from a BenzBoost article in 2011:
As you can see the standard car put down 483 wheel horsepower much closer to the numbers EAS is claiming for the Performance Package E63 AMG although the torque figures on the EAS car are higher. Furthermore, the Performance Package M157 hits 516 wheel horsepower. This is just about the same Insideline hit with their Performance Package CLS63 AMG on a dynojet which was 514 wheel horsepower. For whatever reason, the peak horsepower figures offer a bit of disparity and the M5 being used with a rear section is clearly designed to favor the BMW.
Additionally, the C63 AMG Black Series already comes with stronger internals and a more aggressive tune so there is no additional engine performance package for it. Come to your own conclusion but it sure appears to BimmerBoost that the E63 AMG in the dyno is portrayed in a way designed to favor the F10 BMW M5. It would be great to have the run files to reference as only one pull was not was made. That said, the M5 is the stronger output car stock for stock but with the revised and uprated M157 V8 coming in the 2014 E63 and CLS63 that should all change.