Volo FS3 Fuel Saver Chip/ECU Tuner for 1999 Ford Explorer 4.0L 5.0L This high-speed microprocessor soft-flashes your Explorer's ECU to produce fuel efficiency gains of 15-18% with no loss of horsepower or torque. Installs behind the OBD-II port in minutes. Installation video and vehicle specific wiring print-outs are available on our website. The Volo Chip replaces timing and fuel delivery values stored in the ECU's temporary memory with optimized values. This produces the same results as expensive ECU upgrades, for a fraction of the cost. The Volo Chip DOES NOT alter rev and speed limiters. No fine-tuning or vehicle knowledge required. Just install, hit the reset button for automatic calibration, and forget it. Comes pre-programmed with maps for Ford 4.0L and 5.0L engines. Makes no permanent changes to your Explorer's computer. Will not void your Ford factory warranty and is emissions safe. Best of all, the Volo Chip is 100% guaranteed or your money back! Free firmware updates for life included with purchase.