There are other threads on this. That said, here's cut & paste from one of them:
I have the TRD exhaust. Here's my $.02: know what you're getting. I knew I would not get an American 8-cylinder sound. The TRD makes the Toyota 6 sound decent; "understated" is what I call it. The tip is one of the best. The performance gains, if any, are up for subjective debate. It's a factory option. Good luck.
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'06 Super White Dbl Cab, V6 PreRunner AT, Sport,TRD Exhaust, SnugTop, Westin Step Bars, Toyo Open Country AT's
'07 Sun Fusion FJ Cruiser, AT, UP #2, TRD Exhaust, Roof Rack, Rock Rails, BFG AT KO's