I called Jarco (where I got my clip from) and they said the stock downpipe should have been included with my clip. I picked it up today in anticipation of getting an exhaust system up and running.
The downpipe also came with the stock R32 cat (not positive it's stock though, since the outlet from the cat to exhaust is about 2.75 inches...that's bigger than I would have thought). UPS brought my $300 ebay 3 inch stainless steel cat-back exhaust and muffler today and I laid everything out underneath the car. It appears the stock RB20 downpipe and cat is going to bolt directly up to my cat-back exhaust made for the S13.
I'll let you guys know for sure tomorrow when I actually try and bolt everything up. If this works at least I don't have to worry about getting anything custom to have myself an exhaust, and it will mean that aftermarket 3 inch RB20DET downpipes should also bolt right up
