My GT-R (an R32, mind) was tuned by MRC in Castle Hill, and runs an LTX12 plug'n'play. It has made 262rwkW at 17psi and has good mixtures, runs fine any time of the year, idles rock steady at 950rpm (after disconnecting the idle control valve) and can return well over 550km per tank of BP Ultimate, if you focus on trying for economy.
Seems funny to me how people seem to be bringing up the AFM Vs MAP&TPS thing (like the R32 specific LTX12 sequential fire uses), when this is EXACTLY the thing that makes a D-Jetro set-up better than a normal AFM'd PowerFC (I've seen reports of MUCH better economy with D-Jetro)
Anyway, carry on....