does the van start up idle and pull off ok?or is the loss of power evident when engine is under load at midrange?.your discription lacks this or more info.iam gunna stick my neck out here and suggest starting with the air mass filter/egr valve dirty or sticking/boost solenoid or turbo actuator faulty.faulty injector/solenoids.and of course that all important fuel filter.
tranny granny, December 2011
