[BrianF1960]

An S muffler from 2000 to 2002 models will fit any 2000 to 2002 2.7 with no modifications. 1997 to 1999 2.5 models need an adaptor kit to fit the S muffler (the upper mounting blade changed in 2000). The adaptor kit is around $150.

The 2003 and 2004 S mufflers won't fit earlier cars due to the rear bumper changes and larger pipes.

The S muffler won't add any horsepower as it's a cosmetic change only to have two outlet pipes instead of one. The underlying muffler is exactly the same.