None of the exhausts have been officially released to the public yet. That's why they all say backordered. The first round of orders could be made to Yoshimura on March 29th, but you had to be a dealer. I was able to order mine a bit sooner through Superbike Unlimited, due to them having sponsorship through Yoshimura. But even still, they have not shipped any of them. The production was delayed. I'm not sure about Akra, but it's a similar story with IXIL. Those will be shipping from Europe the end of this month, as per the US distributor that I was in contact with. I was originally going to go with IXIL, but ended up with a much better deal on the Yoshimura.
New bike, new designs... and so we wait...