I've owned both a 6.9 and 7.3 Ford and never really had anything bad to say about them. For what they are designed for they are not a problem. They are not high performance hot rods but I've driven my 7.3 for over 330,000 miles and have never found the need for more power. I've crossed the Rocky Mountains 3 times with it weighing near 9000 lbs. One time me and a guy in a Dodge Cummins got into a duel. I was not fully loaded at that time and we crossed the mountains in New Mexico running about 75-80. Mine was an 7.3 IDI and he a 5.9 turbo but I kept up with him. When I first got into diesels over 40 years ago I learned to be patient. They build their power slowly. At that time I also owned a Ford Torino with a 429 CJR engine so I knew what high performance was like. Now modern diesels are designed to be more like cars in performance.