I have no idea if the exhaust system from head to ball-joint is covered by the warranty, but NOG failed my bike on its MoT because mine was leaking/blowing at the last 2-1 welded joint.
On it's service, a hundred or so miles earlier, nothing was noted.
In your circumstance, that (MoT) might have cost me £600. Based on that, I'd delay the MoT or the whole thing.