Sony hasn't sold disks made by Taiyo Yuden in years. I don't think I've seen any 16x Sony made by TY. And Sony seems to have drifted down into the mediocre range of dvd media lately...no different from the Imation group of companies.
Taiyo Yuden is only manufactured in Japan, so that is one good way to determine if they are TY when purchasing disks, but TY distributes their disks under their own brand That's and under the JVC Premium line. You can also get generic Taiyo Yuden online.
You can find the TY/JVC disks at amazon, but if you are in the US, I'd prefer to order from rima.com or supermediastore.com.