After dealing with this problem for about a year now, a trip to a Freightliner shop and $418.00, I think the problem has been resolved. About 3 weeks ago, I decided to bite the bullet and take the Sprinter to the closest shop 100 miles down the road. After day one, I was told that all hoses and vacuum pressure checked fine, but that one of the mechanics, shop hands, or whatever you want to call him said that he smelled gas in the tank. I knew this was Bull$#!+, because I have had this vehicle for over a year, I was the only one that fueled it and this problem has been intermittent for a year. So, they gave me the great news that they were going to drain the tank, replace filter (which I just replaced), and flush the system (in essesence he was preparing me for a very large bill at a rate of $120/hr labor. At the end of the day, the head shop person said that all that didn't help and it would require further diagnostics. He then proceeded to tell me that it could be a bad injector or cylinder head. Oh, the last thing he said was "it doesn't look good" meaning $$$$.$$. Well, the next week I called the main shop manager that was on vacation when I brought it in and these winners were in charge. Thanks GOD, he actually had sense. It turned out that it was a vacuum box that required replacing. He forgave all the work that they spent draining my full tank of diesel. Another kicker is that I picked up vehicle on a Thursday and the following Monday I rec'd a recall notice regarding the intake manifold replacement. If that don't beat all. But on a happier note, I am very thankful that the vehicle was fixed and just got back from a 2100 mile trip back from Canada without any problems.