That Drain Tube from the Air Filter housing has either a welded tab somewhere in the middle of the Tube or has a clamp. Both attach behind a metal strap below the Turbo.
The tube can come loose from the clamp or the welded on metal tab breakes off (sometimes leaving a hole in the tube).
Both ends of the tube have to have a nipple with an O-ring inserted into them and that clamp in the middle secured in order for it to stay in place.
http://www.peachparts.com/shopforum/diesel-discussion/280787-turbo-drain-blow-drain-seal-replacement%3B-mein-kampf.html