KDX200 & FMF pipe....hhhmmmm,,,,

:bang: Hi, just got a KDX 200 91 model, and bought a Fatty FMF pipe for it(89-94), the only one FMF make they say, but my stock exhaust bolts on and the FMF is spring mounted....They and the bike shops say there is no flange or nothing i can get to fix it....is this a know problem ??

What is going on, anyone experienced this ???
There must be a sleeve or something i can buy to make it work ?

Any help is greatly appreciated.

Cheers