Flip fuel cap on Duster need to be vented?

The other thing you could do if you are "handy" is modify your filler neck AKA weld a fitting into it and remake the old style vent 69/ earlier

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One complication to "not fall into" is that it seems most? all? the vented fillers install from the inside of the trunk, and the cars with no filler neck vent install from the outside of the trunk