1200 adv tank size

i know 33l in book etc... and until 6 months or so ago never put in as much as 33l even when computer tunes 15km to go and te lights are flashing etc... suddenly i seem to be putting humungeous amounts like 34/35 litres and last fill up computer tunes 7km and i put 36 litres..this is at 2 caltex stations (only use caltex these days..cos ucount points) ...so is garage ripping (2 garages) or even if a filler mod done surely wont get 3litres extra that i never got before afaik ...

i do know there is a thread around tanksize but cat find it so plse advise if any