First off, I know for a FACT that at least the 01 GSR had different rotations on the flanges than the previous years - 99- I think. My buddy and I went to install an N1 cat-back on his 01 and it wouldn't bolt up because it wasn't made for the 01, but rather a previous year so the cat flange was at a different rotation than that of the exhaust.

Not everything on the exhaust system is the same from 94-01. Maybe that will give you a little insight.