Well, the truck has about 70,000 miles on it. The first trip length varies from a few miles to 20 miles. The problem starts almost immediately during a second trip. The fuel system has never been cleaned as far as I know. The most puzzling thing about this , is that there are no codes thrown. Maybe because the engine doesn't die? It almost acts as a govenor kicks in at 40MPH. Although, the problem hasn't occurred in a few days.