it's tough in your situation on the 6.4 because there's no way the long block has that many problems. I'm finishing up another 6.4 myself where the guy had a misfire & smoke out the tail pipe. His local "diesel performance" shop sold him a full set of injectors only to come back that it has a miss, so there's probably a compression problem. ...yeah, a big crack in the piston with blow-by pounding out the fill port when the cap is off. How do you miss that and blame injectors? It really surprises me now some of these knuckle heads claim to be technicians/ mechanics with such a great lack of competence.