Code P0741 And Sluggish Running

[wildshot36]

I went to trade in my camper for another and had a 6 hour round trip to do so. The truck, an 06 Sierra V8 - 5.3, drove just fine on the way up, but 2 hours into my return it started to get very sluggish and struggled to maintain 60 on a flat highway. Close to home, the engine light came on. After unhooking the camper, I took it to Autozone and had the code pulled. It was P0741. I then took it to a trusted transmission shop and had them look it over. They went over it for about an hour, test drove it, but didn't find a thing (didn't charge me, either!). They said it might have just been a slip, or maybe the torque converter is going bad and needs replaced. They also checked for any air flow problems just in case that's what caused the power loss. Any thoughts? Camping 8 hours away in 3 weeks and would like to have peace of mind. Also, my camper is 4300 lbs and is only 500 more than the previous.