again from my manual (or manuell in porsche-ese):
Kickdown
The kickdown function is active in selector lever position
D, even if you temporarily change to manual mode
M using the toggle switches on the steering wheel.
- For optimum acceleration, e.g. when overtaking, depress the accelerator pedal beyond the full-throttle point (kickdown).
The transmission shifts down depending on the speed of travel and the engine speed.
Upward shifts occur at the highest possible engine speeds.
These gear-changing speeds remain active until the accelerator is released to approx. 80% of the wide open throttle position.