I have a problem with my 4.8 that I can't seem to be able to find/fix. It basically loses power and will not rev over 3000 rpm. When you gas it over 3000 it just acts like it is working like crazy. It also gets horrible gas mileage when it is having one of these episodes. I call it an episode because it will do this for a month and then go back to normal for a while and then back to acting up. I have changed the plugs and wires, all of the o2 sensors, and took the guts out of the catalytic covertors. Also on this truck it only has an internal fuel filter in the fuel tank. Oddly enough my cousin has a 04 with a 5.3 and he has the same problem. Has anyone ever had this happen?