However, the 3+ cover save for turboboosting has been rolled into the Skilled Rider special ability - which some Eldar Jetbikes (Shining Spears, for example) can get. So, if they have Skilled Rider, then Jink is 4+/3+. If not, then it's 5+/4+.
So trained jetbike warriors
are actually better at evading fire than Guardians! Say it ain't so!