If you don't have any sort of fuel cut or hesitation, keep it off.

Why? Because if it's not preventing the aforementioned, then you can get the maximum ecu output voltage to your injectors without a voltage clamp setting a limit that's possibly lower than max fuel injector output.

Example: (map sensor voltage) FCD sets voltage clamp at 4.6 volts to prevent fuel cut at ~4.8 volts. Max fuel output voltage output is at 4.7 volts. Therefore, at 4.6 volts, you're not getting maximum fuel output (injector pulse) under boost.

(I may be a little biased from my own very long history with bad FCD's)