right now,

1./ poorman CAI

2/. Muffler + 2.5" piping rear end,

3/. Catalytic replacement. Take out the Catalytic, cut a 2.5"-3" Pipe about the same length, find and cut the 2 Adapters look like the front + end of the cat. conv. and welded in with that Pipe, the made adjustment neccessary, then bolt it back inplace of the Cat. Conv.. Keep ya Cat. for Yearly Emission inspec in future.

4/. If I'm right, which likely not. the Cat. conv. of the 03 would be the same as the 98-02, find a used one in the Junkyard, poke a large hole through out it and remove the "stuff" inside the cat. conv. there u go, a plug and play cat flow. This is what i did for my 94 HA, all free.