ok under the manifold there are vacuum ports. i plug the two in front of the manifold going towards the front end of the car. now behind the manifold im using that. what are the two that i plug what are they are what do they do. i dont have any emissions, or that canister for the fuel if the car tips over its. i also pluged the the vacuum line that goes go the map sensor, but i left the port open likes its reading bap cause i swith to mass air. now auto zone told me there is no differances between 86 sensors and 91 sensors is this true