6.4 limp mode?
 

Hey guys at work we have a 2008 f550 service truck obviously a 6.4 and its got a 6 spd manual. Not sure of miles somewhere around 70000. Lately it will intermittently act like it's in limp mode or something but has no dtc or anything. It won't build more than about 15-20 lbs of boost and is just gutless. If you pull over and shut it off and start it again it runs just fine. But if you sit and idle for a while it will do it again or if you short shift out of low it'll do it. All emissions are in place on truck and it will go through a regen just fine or at least according to the dash it does. Any thoughts? Thanks!

Goin limp
 

Might want to check the water seperator sensor. sensor might be bad or the fuel water seperator resevoir needs cleaning. open the water seperator drain valve and see if anything comes out. If not it's gunked up.