Have you considered Compact Motorsport’s Link ECU’s?
It would have to be the best option to ensure the most can be gained from head swap and intake/exhaust mods. And to know you won’t run into any fuelling issues.
Your question about anyone in Sydney being able to tune the factory ecu - I’m not aware of anyone doing that. And as MrG said, Mick’s modification of the ECU is more an overclock of the ECU.