It hasn't got ANYTHING LIKE enough negative front camber to make R888's work properly. Get the Nismo negative camber front arms. Remove the compliance from the front castor rods, wind on as much castor as you can, get some decent dampers on it with some race poundage springs and the car will be transformed. The car may be too low, the kinematics of the stock suspension go to pot if you lower them a lot, they work better close to stock ride height. Obviously you can do a whole lot more, but given a tightish budget that's a good basic track day set up. Toyo R888's are really FAR too soft a compound for an overweight brute like a GTR, when it needs tyres see if you can run to Pirelli P-Zero Corsas or Michelin Pilot Sport Cups, they are chalk and cheese (but a lot more expensive, for a good reason).