I am looking into a Greddy SP2 or Apexi WS catback and wanted to know for sure what modification needed to be done to made either of these fit on a 99.

If I remember correctly it is just extending the pipe a couple inches. Yes? No?

 

I think your right about makeing the pipe a few inches longer.THe 97-99 rear bumber is 1 or 2 inches longer than the 95-99.
THe SP2 sounds awesome. And there is allready a o2 plug for the 97-99 style setup on the 95-96 sp2.

 

Im pretty sure there is no sensors plugged into the catback at all. At least on mine there isnt. Last sensors are in the catylitic converter.

Do you have the SP2? Is there any droning, raspyness, or other rice sounds. I want something quieter.

 

I dont get any raspyness or rice farts. I have it with the Custom Maxima Y-pipe and its very deep. I love it.
I might have a sound clip in a few days if it stops raining down hear in south florida. I can PM u with the link.

 

that would be awesome