++ You would take it off after flashing the ecu for your gearing and nitrous map. That way your ram air compensation works correctly at higher speeds and ensure that you have correct AFR for your all motor operations and then what ever nitrous you want to run compensate for that on the ecu nitrous map.
-- As the bottle pressure gets lower youre likely to need less fuel at higher speeds so retaining TRE would let less fuel come to be delivered to the engine. With lower ET:s you dont need so much ram air compensation and this approach makes tuning simplier for shops which are less skilled and less advanced particularly with ecu tuning.
I always run without tre just to be sure to have right basemap fuel compensation as a starting point, but this opinion is biased.
Hope this helps in making the right decisions for speed and safety ...
