I have an 05 F-350 with the 6.0L and the 6 speed standard. Every once and a while the boost just drops down to 2 or 3 pounds and is gutless but no black smoke. Then either push the clutch in and rev the engine a couple times or shut it down for a minute and the turbo works fine with normal boost pressure. Sometime the turbo will just have a lot of lag and then kick in and work fine. May do it 2 or 3 times a day or not for week. Anyone have an idea of what might be causing this? Any help is greatly appreciated.