I've just changed the exhaust on the ybr 125 fuel injected to a aftermarket Leo Vince one however there was a pipe on the exhaust going towards the air box from what I can make out although I've just left jt hanging as it won't attach to the Leo Vince, it does not effect the performance should I just follow the rubber pipe and disconnect it all

yeah if it looks untidy remove it back to the airbox, leave a little on the airbox and plug the open end off

I've got the same exhaust on my ybr. The pipe is the AIS so just disconnect it. Don't really need to block it off as there's a reed valve.