Is it doing it all the time? I would think if it was bad fuel, it would do it all the time and not just when you go down the highway. I and many other people have had very simular problems. Unfortunately when I brought mine into the dealer, they could not get the truck to duplicate the problem and would return it to me saying it is "NORMAL". I had a no power problem one day I went to the dealer immediately and had their tech drive it. He felt it and low and behold when they tried to fix it the following day, no codes, no symptoms. I got the call from the service writer saying it's OK. I said no, there is a problem and your TECH drove it when it was acting up. At the time, I had no power, step on the pedal and it would barely get out of it's own way. He said he would talk to the tech and get back to me. Well a couple of hours later he called me back and said he talk with the tech and now they remember and it finally threw a code and would be fixed. I got it back and it ran ok for about two months. I took it to a different dealer and they replaced the ebp (exhaust back pressure sensor). Seemed to run ok for a while but now my mileage is about 9.0 mpg average(per onboard computer). I have to really put my foot into it to get it to move. Unfortunately, my wife and I both work and we now only have two vehicles and I can't keep turning it in. I don't let my wife drive the truck because I'm afraid it will act up and she will be in an intersection with on-coming traffic and won't be able to get out of the way.
After this long message, I guess I'm just trying to tell you to make sure you document all the problems well. As you can read in other posts, replacing egr after the warranty runs out is expensive. Ford has a problem with the 6.0 and I think they are doing what they can to avoid recalls.
Yes, I have become a disgruntled 6.0 PSD owner and feel they are junk. Beautiful truck- yes SUPER FAST- yes, super UNRELIALBE- yes.
just my 2 cents