I'm a former owner of a couple 7.3's in the past, test drove a 2003 250 with the 6.0 and have a question. First of all it is lifted, which doesn't matter. It has "NO" power when mashed down from all gears, like a turtle. It doesn't blow smoke or anything, just has no juice at all. I'm thinking of the head, but need some suggestions about what it could be. Over 200K miles, but I've put more on one. Just not farmiliar with the 6.0. Thanks guys.

 

Could be too tall of gear ratio for the tires. Tranny maybe on its way out too.

 

6.0's often have fuel pump problems, especially over 150k and the pumps can get clogged easily. if the fuel filter is not being changed often enough, it will be sluggish. also, if the fuel pump was strained it can make the pump sluggish and slow even after cleaning. the fuel pump clogging can also strain the injectors and that can affect performance as well. hope that helped!