For long high speed trips the engine would be at full power max efficiency with exhaust capable of heating solid oxide electrolyser cell producing h2 and O per electric and water.
Available for 20 seconds at a throttle pop, at a max pressure of 1.45 bar (21 psi), that overboost is essentially the engine's full - time power anyway.
Additionally, IND did one run in 6th gear in full RWD / Sport Plus mode, and hit the speed limiter at about 152mph / 244kph, powermaxing out at 593 wheel horsepower and 578 lb / ft torque.