Some decent coilovers (AP's are good for the money but perhaps a little too soft for the track so KW's or Eibachs if you can afford them) and the ST170 front brake set up, it's fairly cheap to get hold of and 300mm discs are excellent (You'll need at least 16" wheels). Thicker anti roll bars from Eibach or H&R will help keep it flat in the corners, add some sticky tyres and strip it out and you'll have a surprisingly fast car.