Engine Hard Parts Improvements
- Intake Manifolds
- Exhaust & Headers
- Valvetrain & Camshafts
- Porting and Polishing
- Rotating Assembly
- Oiling & Lubrication
- Big Displacement
Nitrous is another option as well, but doesn't seem to have as high of an adoption rate as turbocharging or blower swaps. That's probably mostly due to the limitation of transmission options for serious modders.