I detailed part of the system in the engine thread with annotations on the Ferrari engine. But to recap a major part of the overtake mode is to fully open the waste gate to remove all back pressure from the engine and then use the MGUH to power the turbocharger giving maximum possible power from the engine. This would be in combined with an aggressive engine map and full MGUK power.
The aggressive engine maps used significantly increase the damage matrix and reduce engine life so are used sparingly.
"A pretentious quote taken out of context to make me look deep" - Some old racing driver