No worries - it's probably just because you're still in the early stages of the game!
Light Tuning unlocks in the 4th Race of the 4th Career (B1) Mode, Advanced Tuning unlocks in the 10th Race of the 4th Career (B1) mode, and the OverRev limiter unlocks in the 5th Race of the 5th Career (A/A1) mode.