The B5 S4 2.7T down pipes are a direct bolt on upgrade to the B&B cat back exhaust. Manufactured from CNC mandrel bent T304 stainless steel along with 200 cell high flow metal catalysts these pipes reduce turbo lag, increase spool up for more power and quicker throttle response. The unique two piece design allows the cats to be eliminated with a bolt in cat test pipe for track use. *THESE UNITS ARE DESIGNED FOR OFF-HIGHWAY RACING ONLY AND SHOULD NOT BE USED ON PUBLIC ROADS*