Originally Posted by RDN
You won't lose hp if you get it done at a reputable exhaust shop. I have the dual exhaust set up and it runs clean. If its done right it'll work, I mean look at the s2000 its a four banger w/ dual exhausts.
The S2000's dual exhaust is for style, not performance. I won't help performance at all, it'll probably hurt it. Any time you have a y-pipe welded/installed, then it's going to make the exhaust more restrictive.