My 2007 Tundra pulls 6,200 lbs. quite well. It pulled our 2002 Sunline OK and that weighted in around 8K. I really wouldn't tow anything more than 8k with a Tundra as I think the truck will be overtaxed. If I were towing 8K or more, I would get a 3/4 ton truck for the added payload capacity.
But, I really do like the Tundra. I bought mine used in 2012 with only 20,000 miles on it and it was very well taken care of. It has over 60K on it now and it has been trouble free. The wiper blade connections are finnicky...much better to buy replacements from Toyota. I pland to keep it for a long time!