Toyota calibrated the 2015 Hilux 2.5 D-4D for rugged reliability in varied climates, but the stock Denso ECU mapping leaves conservative head-room in torque modelling, fuel delivery and boost control. This Stage 1 calibration narrows those margins: driver-demand and torque-limiter axes are rescaled for a crisper pedal feel, turbo duty is lifted within safe exhaust-temperature thresholds, and rail-pressure targets are refined to stabilise combustion during rapid transients. Injection timing is advanced only in the mid-range to sharpen throttle pick-up yet preserve smooth idle and cold-start manners. Altitude, sensor-plausibility and limp-home routines stay fully active; if operating parameters drift beyond factory limits, the ECU still intervenes exactly as Toyota intended. EGR flow is reduced with diagnostics balanced to keep fault monitors quiet while maintaining a cleaner intake charge. The result is a Hilux that responds more promptly to throttle inputs, pulls with steadier authority across everyday revs and retains the long-distance dependability required for work or adventure — all without disturbing on-board emissions checks or warranty-critical safety functions.