Hmm over here im running mine on 95 unleaded.
about 130 to fill it up and doesnt seem to last very long.
im running a 265/75/16 tyre as well.

i havent actualy tested mine for how much k's i get per tank etc.
but yesterday i put in $80 was i near the empty line but no light.
ive reset the counter, im gonna drive to the light comes on then record my k's etc
i put in around 44 litres i think at a cost of $1.80 something a litre.

will report back once ive got my empty line on.

mods wise, no cat converter and a custom muffler simular to the pv2. but not straight through by the sounds of it.