I haven't installed on an sxi, but I have run a blaster limited chamber factory pipe on a big pin 750 in an x2.
Lots of people have done the same in X2's with either the SJ chamber or the kaw 650 chamber.
So I can't say anything about how it would physically fit, but it ran well.
It was a pretty heavily modified motor though.
If I were you I'd look at running the waxhead system with the "sxr" chamber.