What is a stage 1 upgrade?

The basic purpose of a Stage One is to modify the air filter, exhaust system, and fuel metering system to run as efficiently as possible, allowing it to breathe freely and, as a result, increasing the available power. Moving more air and fuel through the engine is the fastest (and most cost-effective) was to generate more power and torque. A free-flowing air filter and matching tuned exhaust will add performance you can really feel. Heavy breather and Stage 1 Free Flow Air Filters bring a big boost and a sweet-sounding exhaust system delivers power you can feel across a broad RPM range.

There are different interpretations and variations of what constitutes a Stage One but generally speaking it is recalibration of the air intake and exhaust systems to improve air flow, often using aftermarket accessories that are better equipped to achieve this. One important aspect of the process is that upgrading one part without the others won't give the desired effect. It also generally requires no internal engine modifications.

There are a few myths concerning "Stage 1/4" and "Stage 1/2" but these would be best disregarded as they are a poor substitute for the real thing, and while certainly cheaper, they do not provide anything like the performance increases that you’re looking for. If you’ve not come across these cheap alternatives, they revolve around getting more air into the motor by drilling holes in the plastic air-filter backplate, and seem to work on the assumption that the restriction is getting air to the air filter, rather than getting air through the air filter into the engine.