Thanks for the tip. I was unaware of this vapor return line and will check for it. Upon looking at factory manual it looks like the line routes to the charcoal canister. Easy as unplugging and routing a new fuel line there.
Are you guys installing a one way check valve also along the return line?
Cars with California Emission systems already used the 3 nipple filters- the FSM should show the routing and where they tapped into the line, as well as whether they used a check valve.