Yeah I thought it would be really easy too, but thorough research has led me to finding that the dash harness is needed to do the swap and give the car a factory look. If you are using the Y8 harness, you either must adapt the harness to include the second O2 sensor, or replace your under dash harness. As you may or may not have noticed, there is a rubber seal right about your catalytic converter that houses the connection for the second O2 sensor. This is where the interior harness connects up with. This dash harness is a very expensive item, but im letting it go for pretty cheap.