sounds just like mine lol.
pulled the diff centre out last week, pulled the centre apart only to find it was assembled differently to the nismo expoded view pics.
found workshop manual which then showed it was correct, so figured the nismo kit went together differently so re-assembled it as per the nismo instructions. (all in japanese mind you.)
feels alot tighter on the bench, but ill see how it feels on the track. i tried to find some thicker pre-load shims but they dont do them for the gtr centre, only the gtst. even tried slipping an extra clutch disk in but wouldnt fit.
put a good pair of second hand yokohamas on the front, will chenge the rears after a few skids on the weekend.
also going to wire a reverse lockout button in as im a little cautious when hitting 5th gear as reverse gear is along side it.
it has a lockout solenoid from factory, but only locks out reverse with ignition off. so wiring a momentary switch in so i have to press button to select reverse when ignition is on, otherwise reverse is locked out at all times.