The main warning flag with vortex generators is that they're actually based on antiquated engine technology. Automobiles built before engine management computers became commonplace did rely on the shape and length of intake bodies to manipulate fuel and air mixing. But modern vehicles have computers that constantly adjust fuel flow to match airflow: Create a turbulent airflow in the intake (as a vortex generator does), and the car simply adjusts the amount of fuel it injects [source: Tony's Guide to Fuel Saving Gadgets]. The result? The car may actually run worse, since it's compensating for altered airflow by altering the fuel flow. The computer's fuel-flow rate is calibrated at the factory to provide the right amount of fuel for each combination of driving speed and engine load. Alter this, and you're more likely to hurt performance than improve it