How do I tune an LS swap? (HP Tuners basics)

Every LS swap needs its PCM reprogrammed, even with a stock engine, because the donor calibration includes things your swap doesn't need or have:

• VATS (anti-theft): must be disabled or the engine won't start.
• Injector data and MAF scaling: must match your injectors and intake setup.
• Transmission settings: matched to your trans (4L60E, 4L80E, T56…), or disabled for a manual swap.
• Diagnostics and emissions monitors for components you removed.

Options: buy a PCM pre-programmed for your combination (e.g., PSI Conversion), have a local or mail-order tuner do it, or do it yourself with HP Tuners or EFI Live if you know what you're doing. Any injector change, cam change or AFM delete requires additional tuning.