I don't know about the weight difference of Avionic Nouvelle but the first wave of police 135s (ie. Central Counties, Chiltern etc) have the same role equipment as the Garda machines. Their basic masses are around 1912 kg.
The police machine I have flown normally fly around with 440kgs of fuel, which at 180-200kgs per hour gives a usable endurance of 1hr 50mins with sufficient spare mass to take an additional person (ie. 4 total) from the outset.
If the additional seat is sacrificed (eg. on a pre-planned long search) 2hrs 30 mins plus reserves can reasonably be expected.
All the new 135s will be delivered with the 2835kgs modifications embodied so the picture gets even better.