[MadMotoUK]

Its not a crack, thats just some condensation coming out of the clamp on cold starts. Carbon comes out with the water and stains the pipe. Worst case is that clamp is a little loose and 10 seconds crawling under with a spanner will sort it - dont go crazy, its not meant to be super tight.

Without a better picture, I'm not convinced. It does look like a split, almost like there's a decent bit missing.

 

[MadMotoUK]

This looks like a split to me, if it were a fabricated slit it would be a straight cut.



In any case, surely the mid pipe would fit inside the backbox and the slit would be in the backbox spigot.