could be a mistype (or they could have measured wrong) as they say the pipes are 2.25 to mate with factory manifolds and headers.
http://www.trubendz.com/home.asp?producttype=exhaust&productfor=cougar_ypipe&productid=10010925&pagetype=detail Snippet...
Quote:
This Y-pipe will fit all model year Mercury Cougars, 1999-2002 (also fits the Contour SVT). It features smooth mandrel bent construction for maximum airflow and is made of 2.5 inch, 16 gauge aluminized steel. The front primary tubes are 2.25 inch to mate with factory exhaust manifolds or with headers such as MSDS brand. This Y-pipe comes with 3/8 inch flanges for bolt-on installation. No welding is required. Hangers and brackets are used to attach at factory mounting points. A front O2 fitting is pre-threaded, and a rear O2 fitting is pre-threaded for 2001-2002 owners.
