Differences in '96 and '97-'00 RM125 pipes?

[TheRadBaron]

FMF lists one part number Fatty pipe for just the '96 RM125, and another part number that fits '97-'00. Does anyone happen to know if there is a physical difference of fitment, or is it just different tuning of the pipes for the different porting?

The back story is that I'm having trouble finding a pipe. I think my bike is a '96. The frame number says '96 but there are no numbers stamped on the motor. I think they're replacement cases. I know that the cylinder is a '96 because I put it on, but later ones will interchange also. Anyway, the pipe that came on the bike fits well but is dented up. I bought one for a '96 from a guy, but it doesn't fit into the frame. It's close, but it's obviously a different pipe from the one that I have. It isn't just a matter of the dents and/or a bit of massaging to make it fit. The mounts are different and the shape of the pipe is different. I called FMF with the part numbers for both pipes, and they BOTH came back as being for a '96 RM125. Hmmm....that can't be. They're differently shaped pipes and one doesn't fit. FMF sent me some pictures of a '96 RM125 pipe that they have, and it looks more like the one that doesn't fit (though it's hard to tell in pictures). I'm thinking that maybe I need the '97-'00 pipe, but I've been closely looking at photos online and I can't see any reason that the pipes would be shaped differently.

My concerns are that I might get the wrong pipe again and end up paying a bunch of money shipping it back and getting another one. Also, if the difference between the two part numbers is the tuning, I don't want the wrong pipe that's optimized for different porting.

Anyone have any insight?