^^^ In my opinion, the hybrid and the justjap kits do the same job at the end of the day.
I did an install for Gengis yesterday at his work (got shifty looks by some), and he bought the justjap kit... If you refer to his FMIC installed thread, he quotes that the car feels more powerful at the top end from the cooler, however you get abit less lag from the start. This is due to the extra volume you are trying to fill up when boosting, hence some guys tend to wind up the boost another PSI or so.
For the GTST, either the hybrid or justjap one is the same amount of time/ease to install.
By the way, you dont have to head out my way, I come out to you providing your in Sydney