I sold my 99 Si about 4 months ago and have had my WRX for about 3 months. Putting exhaust on a civic is so much more different than a WRX. Stock WRX has a total of 3 cats and 1 resonator going from 1 in the uppipe (before the turbo) and 2 in the downpipe. Thats alot of restriction especially for a turbo car!
here is a link of a great diagram of the stock wrx intake and exhaust!

http://www.scoobymods.com/forums/sho...?threadid=1575

just my .02
JT:thumbup: