According to both Bassani and some others who have posted, the 01 system will fit the 03. Bassani has a specific 03 application in the works. It may have already been released.
I put the FR500 cat back on my '03 two days ago. I'm unimpressed. Major drone at 1800-2000 rpms, no growl anywhere. Big time expensive. I'm wondering of the stock catback wouldn't be better, provided an O/R H pipe was used?
That's what I have on my '97, and I love the sound. Sure would like to stay smog legal, though!
Later,
CW