Fuel Problem?

[LA Pressure]

I just started noticing this here recently in my 01 7.3. I own a pressure washing company and fully loaded, my trailer weighs about 10,000 pounds. When I get on the interstate trying to get up to speed, once I get to a little over half-throttle, it seems as if I can't get any more power. You can put your foot in the floor and it will keep slowly gaining speed, but thats it. The rpm's don't change or anything. So, the next time I dropped my trailer, I tried it again empty and it did the same thing. Once I get up to about 55/60, I can't get any thing more out of it. It's like it doesn't respond to what I'm trying to get it to do. Checked the computer and no history codes are showing. Could this be a safety thing with the computer or what cause it sure as hell doesn't seem like that's what it ought to be doing.