You're not going to really see any gains or changes from that, unless you just want two pipes coming out of the back, it's really pointless. You can get a shop to custom fab you a real dual exhaust, with an X or H pipe for like 500 bucks parts and install, and it'll actually make a difference. That dual exhaust conversion kit does nothing because when it hooks up to the factory Y-pipe, you get essentially the same restriction because of the connector where the Y would come down to the single pipe out. With an X or H pipe you dont have that area of restriction because the pipes are consistently separated or wider, allowing for free-er airflow throughout the entire exhaust.
tl;dr- Don't get a dual exhaust conversion kit, get a real, practical dual exhaust for not too much more.
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