JET Performance under drive Pulley Kit offers easy horsepower and torque increases for your vehicle. It provides an exclusive full range tuning of the air/fuel ratio, ignition advance and various other parameters. Each tune is track and dyno tested to ensure the most possible horsepower from each application without effecting drivability or fuel economy. The stage 1 chips are designed for using lower octane fuels. The stage 2 chips are designed for using 89 or higher octane, improved air intake system, improved exhaust and will work well with a 180 degree t-stat. The stage 2 will also work well with aftermarket mass air sensors, tbi spacers, etc.