Overboost

It makes sense to provide plausible engine fuel and ignition mapping to the limits of the factory fuel injectors, which would typically be sized sufficiently large to provide optimal fuel to the airflow/boost limits of the stock turpocharger even though the wastegate should normally prevent the engine from boosting so high. This is because the engine can overboost if the wastegate manifold-pressure reference line is cut (melted, crushed, disconnected, and so on), and a "safe" calibration -- even in forbidden overboost territory -- is one more countermeasure designed to help avoid engine damage from lean mixtures if the engine does overboost if fuel cut strategies fail.

Morgan was waiting outside in the bay. Didn't even wait for me to say a word. "What happened? Why did you overboost? You could have blown the whole shuttle, the whole expedition."

Overboosting is not something that “just happens.” Usually, it's under the control of the pilot, or can at least be prevented by an alert pilot.

These planes all have popoff valves, designed to prevent overboost, but the flow dynamics are such that manifold pressure can seriously overshoot redline before the popoff valve opens.

A manifold pressure overboost control is usually employed to reduce the possibility of overboost occurring. However, when overboost occurs, combustion temperatures rise, and detonation or preignition may result and cause serious structural damage to the engine.

Manifold pressure exceeding the limit lines shown in figure 5-2, constitutes an overboost.

By delaying opening of the wastegate, the ECU could generate an overboost at full throttle, increasing boost pressure to 1.1bar, for a peak power delivery of 230bhp in short bursts of up to 30sec at a time.

Also, be careful you don't get an overboost or too much RPM when you reselect cold.