I am not new to trailer towing, far from it actually. I have a class A CDL with over 200,000 miles under my belt. My trucks towing ability, or lack thereof, has me wondering if I've been doing it wrong. With my fifth wheel, my GCW is around 16,000 pounds yet my truck seems to always struggle with it. It doesn't struggle in the suspension or the ride but it seems like I'm down on horsepower compared to other 99+ 7.3L trucks. As an example, I was heading up I 25 from Denver to Fort Collins. While there's no major hills on this section of road there are a few areas in which I have to take my truck out of overdrive. In doing so, I bring the revs up to 2500 and bring my speed down the 65 mph. While I was chugging along I noticed a truck very similar to mine pulling a much larger fifth wheel coming up beside me. While the truck wasn't at light speed, he was definitely in the 70 – 75 mph range. Just as the truck got my side I looked over and noticed a couple with the combined age of nearly 300 years. The truck had no gauges and from my vantage point, appeared perfectly stock. As I let the truck move over in front of me I put the hammer down in an attempt to keep up with him. While I typically don't like letting my truck rev over 2500, I brought it up to 3000 just to see what would happen. Even at 3000 RPM, the old man and his Ford walked away from me. While I know I have a slight leak in my up pipes, would this rob me of enough power to keep up with the heavier rig? I am very pleased with my DP Tuner and its abilities to keep my EGT's manageable. There have only been a few times when I've had to come off the throttle to keep them in check. Usually this is only because I'm driving into a stiff headwind. My truck has spent the last few years as the tow rig for my excavating company as well as being the family truckster towing the fifth wheel for our vacations. Are there any modifications that won't break the bank or require a complete engine rebuild that would make my truck a tow monster? I'm not talking about being able to tow 50,000 pounds at 100 mph but rather being able to tow a fifth wheel that weighs around 10,000 pounds without having to kick out of overdrive at every overpass.