Tuned sealed airbox + ram air = more HP
... one factor to a quarter mile pass in the nines.
Another factor of course is the longer wheelbase enabled by the extended swing arm - whether aesthetically pleasing or not, functional to attaining greater control in keeping the front wheel down and preventing a wheelie during the launch, which is key to attaining a quick as possible 60 foot time, crucial to running the quickest quarter mile time. Wheelie upon launch = slower E.T.