I have a 2005 Tundra Double Cab LTD and was looking to modify the exhaust system. I have a local muffler shop close to my house that I trust and when I talked with the manager and described what I wanted to do, he recommended the Flowmaster 50 Series Delta Flow. After reading the advice on here, which is volumious and varies greatly, I made a decision.
Now, I was not looking for gains in performance or gas mileage but I didn't want to lose anything in these areas either. I simply wanted the truck to look and sound better. The only thing I did differently from what the shop recommended is I went with 2.25" pipes from the Muffler to the tips instead of the 2.5" that they recommended. I picked up the truck today and spent about an hour driving it under different road conditions and speeds (with the exception of towing). I am EXTREMELY pleased with the choice I made.
The shop finished the 2.25" pipe with 3" chrome plated stainless sausage tips that exit behind the rear tires at about a 45 degree angle. They extend just beyond flush, maybe an inch or so beyond the quarter panel. Far enough to add nicely to the look of the truck but not far enough to bump into when walking by. All of the 2.25" pipe is completely hidden under the truck and only the tips show from the back end view.
Performance-wise I have noticed no loss on the low end and the truck seems to respond better in the mid to upper RPM range. The sound is very, very nice

. Relatively quiet but bassy purr at idle and a nice, deep, aggressive sound on acceleration! I did notice a trace of drone in the 1.5 - 2k range when I first started driving the truck after I picked it up but after the muffler warmed up there was absolutely no drone at all. The only time I knew that I had modified the exhaust was when I got on the gas and that was music to my ears my friends
Thanks to all who have posted on here with regard to exhaust mods on the Tundra, there is truly a wealth of knowledge here. My advice to anyone considering an exhaust mod would be to invest some time in reading through all of the threads, it is time well spent. For what I wanted out of the mod, I think that I achieved success.