The GTR ECU can work and it uses MAF not MAP sensors and can be remapped but the cost of everything inc GTR heads is nuts for the power you will get.
Just fit a Good turbo and ECU plus good exhaust and cooler and you have a safe 330+rwhp using the RB25.Total cost of around $6-6500 but the GTR setup would cost around 13k all up inc exhaust cooler head labour gaskets etc and then you still have a 2nd hand turbos,ECUs head ETC.Your comp ratio will be low also so you should really change pistons etc.
Not the best way to do a budget performance upgrade as even a complete RB26 import motor would be cheaper.
Copy Shutto boys old RB25 setup as it made 360rwhp and was a nice car to drive.