My advice is to have a good shop make you up a custom downpipe man. I personally bought a CMPE downpipe through tunersnation that was made for the Evo III O2 housing and was very, very disappointed. For one the quality of the welds is pretty bad, next you have to buy their "test pipe" in order for it to extend to the catback, and the fitment itself is crappy.
The flex section on the downpipe fits between the tcase and the oil pan sump, the problem is that there is less than the width of ONE human hair between the flex and the tcase, and on the other side (between the tcase and oil pan) there's about an inch and a half. The damn flex touches the tcase the whole time and basically superheats it! Shoddy. Especially for a DP as pricey as that.
EDIT>>> Excuse the poor photo's, all I had was my phone so I just snapped a pic with that. Interestingly enough in the pic it doesn't look toooooooo bad but when you're underneath the car you literally can't fit a hair inbetween the flex and tcase, and this is their DP made specifically for the Evo III O2 housing which I'm currently running.
I won't even get into the catback details..... /ubbthreads/images/graemlins/banghead.gif