If you want to get more torque, power and MPG in your Toyota, chip tuning/remapping will give you the solutions you are looking for. The two procedures provide similar results. The only difference is that chip tuning is applied to vehicles made before 2000, while remapping can be performed on new, post-2000 models.
Chip tuning involves the removal of the Engine Control Unit (ECU) from your Toyota and reading an EMPROM (erasable programmable read-only memory) memory chip on which the auto manufacturer has stored various performance-governing values. These values are set to a generic level, however, and do not consider your unique driving circumstances. This is why changing the values via chip tuning will provide performance improvements - they are customized to your needs. Once the ECU is removed, the chip is also removed, it data is accessed to determine its original values. Then the chip is reprogrammed with the values that are more likely to deliver the performance you want from your vehicle. The chip and ECU are then reinstalled, and you are on your way to enjoying a better, more fuel-efficient ride.
Remapping provides the same kinds of performance improvements as chip tuning, but the procedure is a little simpler. For post-2000 Toyota models, the chip in the ECU can be access through an OBD/OBDII port, which eliminates the need to remove the unit from the vehicle. All changes are accomplished electronically through the diagnostics capabilities of your Toyota.
Once the changes are made, you will see more throttle responsiveness, better fuel economy, and a much smoother ride. Any alterations made to the performance values are well within Toyota's safety parameters, so you have no need to worry.