Hi,
A 2006 F-350 4X4 dually 6.0 liter completely stock current owner. I have NOT read this entire thread as it's getting pretty long on the tooth. I will say we are happy with our truck, currently 126,000 miles on it. I do my own regular maintenance on it changing synthetic oils and filter regularly. Last year, we were hauling our Eaglecap 1160 and heading from NH to AZ when the check engine light came on while in CT. I monitor engine oil and water temps with a scan gauge. When the light came on I checked the code being displayed and it indicated that our turbo was in an under boost situation. I noticed nothing unusual with engine performance or anything else. So we continued into NJ when the the truck went into Limp mode reducing engine output. It was on a Sunday and we started looking for a reliable FORD diesel dealership. We limped to a dealership and they took us in the following morning. They're engine code scan tool revealed and over/under boost on turbo and we'd lost #7 injector. Replaced both at $4K and we were on our way. Never had a problem before. Has been a great truck. Do your research, if you find a used one, get the VIN and do a "OASIS Report" search for warranty work done on it. This will give you a heads up on potential problems on the truck and decide whether or not to walk away from it. My advise is to keep the truck stock (no chip or Edge) and do regular fluid changes. Monitor your engine oil/water temps. Coolant filter is a good idea as well.
Good luck with whatever you choose to do. We have enjoyed ours and would recommend it as long as your not trying to hop it up in the horsepower realm.