One side on each head goes to a sensor the other I forgot I think the evaporative canister. Take the one side to the emissions out and put in a small bolt medium lock tite in its place. Forgot the size but keep it small in length to avoid having it stick out into the intake and disrupting airflow. Or just glue gun the hole in the nipple but it might make someone later think some hose is missing. It’s not very technically advanced. I think it’s just ment to suck fuel fumes from the evaporative canister back into the engine. Don’t as some people have run a hose connecting the two heads.