My 6.0 went goofy the other day. Normally when I pull anything or use it on the highway it has awesome power. But after filling it was really boggy at start up until about 20 MPH. It hardly had any power at all at low speeds. I got mad at it and revved the engine for a few seconds and noticed black smoke from the exhaust. Then it seemed to run better, about normal. I wonder if it could have been bad fuel.
Anyone else experience this kind of problem? If so, do you have a solution?