Sounds like you've tried a few options with the carbies Stu???
Cosco is the best tune up here.
The last 6 months it doesn't matter how aggressive I ride, fuel has been a flat rate of $1.33/Litre.
But I found gains in fuel consumption wise by activating the TPS on the prog ignition, running dynatek DC-3 coils, even the catch tank gave added improvement with the carbies not sucking in all those crankcase fumes.
These are all noticeable changes especially under 3-4000rpm in performance, so If doing a lot of commuting and day to day riding, I can see you would get value from the coils and catch tank alone.
The ignitions performance have sold themselves .
I cant really give you a mileage per tank though as I've changed gearing so much from 17 and 16 fronts and 39-40-41 rears.
Current 16-41 is 4000rpm-100kph in top gear.
It doesn't matter what stage of tuning your TRX is, get the fuelling and timing close to optimum and you will find really good gains.