When adding an AFR module to monitor your fuel mixure or use the Closed Loop System, the module plugs into a 2 pin connector at the bottom of the factory harness near oil level site tube on the outside of the chaincase.  Certain model years may have a heated rollover valve which is already plugged into this connector.  If that is the case, this Y-harness will allow you to connect the AFR module as well as the heated rollover valve so that both will function.