(19 Apr 2016, 7:46 pm)Dans_bus_photos wrote Is the PVR of the X1 reducing? Since 6001-3 and 3943 are the only ones to have received advert boards and have not been branded (as of yet), where all the other repainted B9s have gained the new branding
No, it's not.
It has been explained by busmanT in the past why 6001 - 6003 have been fitted with advertisement boards. This post has been quoted/linked on a number of occasions since originally posted - someone may be kind enough to do so again.