Well I guess I'll start off by saying I am 17 years old and I have owned my 03 7.3 PSD for about 5 months now. I have the zoodad mod, foil delete, factory straight pipe with size exit, blah blah all of the cheap stuff since I only work during summer. The truck is an auto and has about 137k on it. From all the research I have done PHP is the tuner I want. I've narrowed it down to the Phoenix chip. I *think* I want 1. stock 2. 40/heavy tow 3. 80/light tow 4. 80DD 5. 120 race and 6. smoke show. I tow a +/-6000 boat depending on what were doing about once a week. I will tow bigger loads every once in a while. This truck is my daily driver to school. I do not trash my truck, I want it to last for a long time, so obviously I'm not gonna roll up to every stop light and put it in 4 hi and on the 120 tune and take off all the time. What kind of MPG improvement will I see with the 80 DD? Any suggestions for me? Is this tuner just a knob you turn for each tune? does it plug in or what? What are the downsides to having this tuner? I can't wait to roll up to all the other kids who think they are bad with their civics and coffee can mufflers and smoke them out when they think they're bad. Thanks for any info.