How to Get More Horsepower Out of a Nissan Xterra

Swap out the Xterra's old stock air box and intake and replace it with a short ram air intake with a conical filter. The old plastic air box can be removed by unbolting it with a wrench, revealing the throttle body underneath (which leads air into the engine). The new short ram intake can then be attached to the throttle body using a rubber coupler and clamp, which you will tighten with a flat-head screwdriver. The advantage of the new intake is airflow. The ram air intake will bring in more air than the restrictive stock air box and air filter and thus provide more oxygen for the engine to burn.

Replace the Xterra's old muffler with a performance muffler. The Xterra's stock muffler has an opening of only about an inch and a half across, which restricts gases trying to escape from the engine. A performance exhaust, however, usually has a diameter of about 3.5 inches, meaning more air can escape, the drawback being increased engine noise that you may or may not find desirable. Removing and attaching a new muffler will involve sawing and welding, a process that should be done by a professional mechanic unless you have experience with the practice.

Install a performance chip in the Xterra's Electronic Control Unit (ECU). A performance chip is essentially a resistor that tricks the Xterra's computer into providing a more efficient fuel ratio to the engine, thus increasing the horsepower. Installation of the chip may vary from manufacturer to manufacturer, but it typically involves inserting it into your temperature reading unit in your air intake or directly in your ECU. Using a performance chip will give you more horsepower and will usually also increase your fuel economy.