@dportero well you could try manually tweaking the parameters from the heater tuning to try and get a tune that works better at the higher speed, though this may mean it is less stable or overshoot at lower speeds.
Probably worth trying to identify what is causing the temperature drop too. Is it from melting that much filament, e.g. try extruding that volumetric flow when stationary? Is it from the air flow during movement, e.g. try moving at 400mm/s? Is it from the cooling fan kicking in at a higher rate?
You could also try fitting a silicone sock if you haven't already?
