The nearest to you Yousef will be Just Engine Management at 2/2 Noonan Rd Ingleburn.
Talk to Adam there about what your needs are.
Then buy the parts you need for 1 complete set of tuning.
If you want a second opinion, try Unigroup Engineering at 17/17A Amax Ave Toongabbie.
Talk to Yavuz about what your needs are. Mon/Wed/Fri he's there. (Tues/Thur, he's at South Windsor branch)
For servicing your car, the hourly rate is cheaper at Japlink 21 Bridge St Rydalmere.
They look after SAU Members and charge W/S for Nismo products; but they may take a while.
For immediate spare parts, new - contact Just Jap at Kirrawee.
For used, try Skyline Spares at Wetherill Park
For new spares overseas through SAU Traders, contact elrodeo666 or Kudos or Jesse Streeter or Import Monster
For new spares online, try perfectrun or rhd
Welcome to SAU!