My Duramax is 9 months with 19K miles. I drive the truck at least 85 miles a day to and from work. It seems to run perfectly fine. However, on weekends I pull a fifth wheel travel trailer that weighs around 9500 - 10,000. When pulling the trailers to the camp ground it seems as though it is weak on power. At speeds of 65 to 70 it seem as though there is not a lot left. On the return trip it may be my imagination, but it seems to have much more power?! Is this the transmission monitoring my daily travels? Is it an injector problem? My daily commute speed is approximately 60mph.