They're not only different, I don't know how he took one off a GS-R, as it wouldn't fit on an ITR???? I think perhaps just the top piece might, though I've never tried...but for sure the bottom piece is a different length due to the cat...or at least mine didn't fit on my friend Mike's 96 GS-R...Either way, it doesn't flow as well, and doesn't have the same size primaries or anything else for that matter...I think in this case you placed your trust in the wrong person...

Some one correct me if I'm wrong???

Later,
Aj