Enrico Benzing, a famous Italian engineer and journalist (not the first biased bloke behind a keyboard), claims that the TagHeuer Renault benefits from an improved fuel flow in qualy. Every kg/h over the allowed 100 and over 10500rpm gives approx 10HP more. He compares it with the mother Renault and also analyses the Merc-Ferr-RB improvements.
Even factoring the RB aero efficiency, also most of us on this forum didn't expect a RB-Ferr gap so strong in favour of RB