I just bought a 2015, and while searching for a rattle, I was removing the exhaust and noticed there was a butterfly valve on the pre chamber. No cables were attached to it so it is just permanently open. What exactly is this used for, and is it necessary to replace the missing cables?
That valve is used for noise abatement. It's opened and closed by an electronic motor in the tailsection through push/pull cables. It's spring-loaded open for failsafe reasons. It's a common mod to remove the cables and leave it open all the time. Forget about it and enjoy the ride.