There are different grades and qualities of stainless steel. Lower grades can rust. Hate to say it, but the TRD on my '05 had surface rust. For the most part it polished of but after awhile it started leaving marks where the rust was. My '07 has the stock exhaust for now, but I have to say I miss the sound of the TRD with or without rust. I don't know about the borla, but my TRD exhaust wasn't horribly loud until you stomped on it. If anyone wants to hear the exhaust sounds of both these systems, I had come across them on
uTube.com Universal Tube & Rollform Equipment Corporation - Tube Machinery - Used Tube Mills, Used Pipe Mills, Emmedi Welders, Rollformer . Search under Tundra, you'll have fun watching some of the videos while searching.