Hello

I have a 08 f350 180,000 miles. It has a darkknight tune , with dpf delete completed, egr work done through the reprogramming of the truck last year. no problems previously towing before a couple of months ago. I have an issue when towing my 5th wheel trailer lately which is about 13,000lbs. I replaced my intercooler at beginning of summer, K&N Filter. Without the trailer I have no power issues at all at any speed and when I it the pedal it goes full turbo. With the trailer after about 10 miles I lose all power on the highway. The turbos will not go above 20 psi when this happens. If I pull over and turn truck off for 5 minutes and start to go the same cycle occurs after 10 miles. There are no drivetrain or any other codes thrown.
i will be replacing the low pressure fuel, IAT@ and MAP sensor hopefully this weekend. Any other ideas