I have a Borla x-pipe assembly P/N 60089 for 2005-2008 C6. This unit has less than 100 miles on it. It is in absolute perfect condition. I decided to go with long-tube headers and that is why I am selling it. $175.00 firm, plus shipping from Seattle (98108). This does not fit Z06 models.
Yes, it is a direct bolt-on replacing the stock H-pipe. As far as HP gains, it is supposed to add a few HP. It also reduces resonance in the system and the X section combines the two flow passages together so that the higher pressure in one pipe can bleed off into the other. This smooths out the exhaust sound. NASCAR teams and other forms of racing use them.