As these vans age we are seeing this more and more. The old Windstars had their own issue with lean codes P0171 P0174 and now the Freestars too. What happens is over time the rubber degrades in the PCV tube and a hole is created causing a major vacuum leak. If yours is running poorly or has a roiling idle this is worth a check as it is quite common. The hole may not be as obvious as the one shown in the video but the last shop that looked at it overlooked it so it is possible. Take a look.