Well from quite a few accounts, the GTR gets faster the closer to 50/50 torque split it gets.
There was a certain R32 GTR sport sedan, where the team solid locked to 4wd system to 50/50, and went 1 sec per lap quicker, only problem was it would break the front diff housing off the sump under brakes as it couldnt handle the stress.
The GMS GTR's ran a lever in the cabin to manually adjust the torque split.
In the Skyline Chassis the 4wd system simply works better than RWD only, infact works better in most cars.
There was a reason Colin Chapman started building 4WD F1 cars in the 70's until they too were banned.
WRX's understeer like a biartch from factory, but fit a helical front LSD and they turn in like a deamon.
The aftermarket can fix most AWD/4WD shortcomings that factory standard cars have, ala: WRX and early EVO's, GTiR pulsars etc.