Guys, Standard ECU's cannot be remapped just as they are.
What you need is what the Japanese call ROM Boards. You will need to buy a ROM Board and then have the proper extraction and installation tools to replace the STD ROM Board with your tuned ROM Board. This is what the Japanese refer to as "ROM Tune" ECU's (Mines, Kakimoto, Brain etc....). By doing this your car can be tuned for mods while at the same time retaining all the factory advantages such as fault compensaion, air conditioning, idle control and auxlaries (e.g. R34 GTT Auto Gearbox).
I'm fairly sure this is what Ed is referring to as "Daughterboards". Correct me if I'm wrong please Ed