Holley Air Temp Sensor 554-121 | Make sure that your Holley Terminator EFI setup is running at the optimum level with a new air temperature sensor. These parts originally come with the Holley Terminator EFI kit, but over time, the sensor will need to be replaced to keep your system running smoothly and reliably. Continue with the added benefits of EFI by replacing your Terminator air temperature sensors when the time comes with genuine Holley products.