There's a discussion of this issue here:

http://www.bonnevilleamerica.com/forums/...rt=all&vc=1

What I took from it was if you have chambered baffles, you need the crossover.
With open pipes, you don't.

This is an open item with me today too.
I'm having some alignment issues, and the presence of the crossover doesn't help.

Said Molly to James, that's a fine motorbike. Richard Thompson