engine light comes on and engine power lose
 

I have a 2004 Chevy Silverado 1500 2 wheel drive extended cab with a 5.3 engine on resent vacation while towing my camper I had the engine light come on and when I exited the interstate the Truck wanted to stall. I stopped at 2 garages and both places told me after hooking hooking up to the computer that it had multiple missfires and the o2 sensors were not working correctly. after clearing the codes it ran fine with no problems over 2 days of driving around with no problems, no light no misfires, I hooked my camper up and started home about 2 hrs into the trip home it repeated the problem again, can anyone help me figure this problem out