on a 6.0 with 42 lb injectors will not be enough. I went to speed density and cos for my truck and I might make 475 hp. I would find a different tuner. the old tuner could have set a fail safe to pull timming if the map pressure got to high, so he could save your motor. I would say have someone look over the tune and log it! If they have a clue then they can atleast tell you whats up!