I used a magnaflow Y pipe and reversed it to use an 18" round magnaflow and it just wasn't loud enough for me so I had it straight piped and it sounds great now, but magnaflow does have a dual in/ single out that worked great for the Titans, again not very loud but i went from a staight pipe to that particular muffler on my Titan and the bottom end was a lot stronger.
http://www.toyotatundraforum.com/exh...installed.html
http://www.toyotatundraforum.com/exh...ision-1-a.html

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07 Silver Tundra DC 5.7L-Custom Exhaust-Limo Tint
Headlight Mod(Black)-Blacked out Emblems-24" Boss 330s