The most basic computer upgrade for your 4x4 is a chip or module. These work by translating or tricking the messages from sensors on your engine such as throttle position and mass airflow, and telling the computer running your fuel injection to adjust timing and fuel flow. Most chips of this type result in gains of 25 hp or less. We found that sometimes the gains are hard to notice, since a slight increase in power can be less than obvious. If you are doing a seat-of-the-pants dyno, try removing the chip, because a reduction in power is more obvious.