I have a F-350 crew dually and I'm having some problems with it surging at a crusing speed. Even through accleration unless I punch it hard. I can hear the turbo whisleing up and down aswell with this surging. Also under load ( towing) if I get on it hard at just befor it shifts (higher rpms) the turbo almost sounds like it rattles or something. The truck has only 24,000 on it. Now to compare these smptoms I have a F-250 company truck 2004 with the same 6.0 diesle package in it. It has 181,000 on it and it does not do any of these things. This truck towes constantly (boats) Please let me know if you have had the same or similar problems.