Well the SVO Y-pipe does not just "bolt up" to the stock 2.3L cat pipe, that's the main thing. The curve on the y-pipe is different or something.
At any rate I had to take it to a muffler shop and they ended up cutting the ends and welding on new ones to make everything fit, I couldn't get it to work right myself (of course, that was quite a few years ago when I didn't know quite as much as I do now)