I have the same IMPUL ecu in my car.
I personally wouldnt bother with a retune. Think of it this way - if there is only once place in SYD who would do it, then you will basically be stuck with them forever.
If you grab something like an e-manage, haltech, or other generic piggy back solution, you'll be able to get it tuned basically anywhere. Important if you ever do any more mods in the future.