From GTPlanet Game Guides

Modifications

Oil Change
Racing Exhaust
Racing Chip
S2 and or R5 Tyres
Stage 3 turbo
Large Racing Intercooler
Brake Balance Controller
Racing Suspension
Fully Customisable Transmission
Triple Plate Clutch
Racing Flywheel
Weight Reduction Stage 3
Port Polish
Engine Balance
Stiffness & Chassis Refresh
Fully Customisable LSD

My car is also fitted with aftermarket alloys and a wing, no downforce is used in the settings below as the car doesn’t reach speeds at which is would be of great effect. Therefore these two modifications are purely cosmetic and can be omitted if required.

Settings

All are shown Front then Rear

Spring Rate – 4.0 / 4.4
Ride Height – 115 / 115
Bound – 1 / 2
Rebound – 2 / 4
Camber – 2.0 / 1.0
Toe – 0 / 0
Stabilisers – 2 / 2

Downforce – 0 / 0

VCD 10 / 30 / 20

Brake Balance 4 / 3

Gearbox – Auto 10
Be careful if changing gearbox settings as Auto 10 helps to keep the car right in the powerband.