A complete exhaust system will net you around 10-15 HP on a stock motor - maybe more, every setup is a little different.
Equal-length shorties will give you slightly more HP (scavaging ability) but will also be a little more PIA to intall. I have BBK equal length's, BBK off-road H-pipe matched with Dynomax 2.5" super turbo muffs with the stainless steel pipes. I really like the sound and the quality is very nice, IMO.
If you have any more questions, feel free to ask. This is a great site with great members and moderators. Enjoy your stay!
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