More Tuning Upgrades

[BJahalt88]

I'd like to see some tuning upgrades from GT1 to GT5 make a return to GT6:

• Engine Balancing upgrade. (GT1-GT4)
• Sport/Semi-Racing/Racing Flywheel upgrades. (GT1-GT5)
• Displacement Increase upgrade. (GT1-GT4)
• Sport/Racing Intercooler upgrades. (GT1-GT4)
• Port Polishing upgrade. (GT1-GT5) [Note: called Port Grinding in GT1]
• Heavy-Duty Single-Plate Clutch upgrade. (GT1-GT5)
• 1-Way/1.5-Way/2-Way Limited-Slip Differential upgrades. (GT1-GT5)
• Sport/Semi-Racing Suspension upgrades. (GT1-GT5)
• Original Suspension/Turbo Kit upgrades. (GT4)
• Stage 4 Turbo Kit upgrade. (GT4)