if you get 200kms from either the top half or bottom half of the tank your doing very well.
melbourne seems to have better petrol than sydney - i always read skyline melbourn'ites averaging over 400km a tank which is around 12l/100km's, which is doable i guess...im more 12.5-13l/100km. around 400km is my average.
i have powerfc, 13psi boost, full exhaust & hiflow cat, front mount, hiflow filter element. the powerfc makes a large difference, before the PFC i was averaging about 350km per tank.