This EJ205 also has the AVCS choice to operate For added general performance. To run the AVCS, the avcs harness as well as avcs ecu is required. On the other hand, This can be optional, you don’t really need to run the avcs to help make the motor in good shape in your 2002 to 2005 WRX. It is a immediate prolonged block substitute for 2002 to 2005