How many miles on the air filter Ed? The diesel vans don't get the better Donaldson filter like the pickups/Excursions because there is not enough room for the bigger airbox.
Ford recommends checking the filter minder on top of the airbox every 7,500 miles and changing the filter only when it goes from green to red.
You can squeeze a few more miles out of the filter by taking it out and tapping it to knock the big stuff off the outside. Some even use compressed air on the inside of the filter to blow the finer stuff off the filter fabric. Make sure you don't rip the filter with too much focused air pressure.
However, the filter is a bit of a PITA to get out and you may not want to monkey with cleaning it when you can replace it for $22. Check out dieselfiltersonline.com http://www.dieselfiltersonline.com/F...r-Fa-1804.aspx
. About half of list price. Good site for all your filter needs.