Now the S63TU twin turbo V8 will obviously see gains with an ECU but tune, intake, and exhaust but what is being depicted here is insane. GermanBoost network member @Pea was at the event where these Manhart tuned M5/M6's were running and he was not allowed to run them as they were making excuses.
Were the opponents hand picked to make the M5/M6 look faster? A P31 C63 AMG recently beat a stock F10 M5 in a half mile roll on race yet here we see a tuned M5 absolutely crush a C63 AMG Black Series? A tuned M5 should win, no doubt about that, but not by instant bus lengths. The C63 never sounds like it is in the right RPM and actually sounds like the transmission has to kick down a gear before accelerating essentially giving the M5 a giant jump.
This is yet another video from the same source that wants to portray the M5 and M6 as faster than they truly are. This would not be the first time a race was staged by this person for this purpose. Notice we never see videos of the tuned M5's or M6's at the events losing? Well, that's because Manhart sponsors the forum where these videos are published and it's much better for sales to show the cars doing what you see here below.
Come to your own conclusion.