Ferrari are about to use their last development parts in written form, but the team decided against introducing it on track since it would have resulted in a grid penalty.
Formula 1 teams were allowed to develop their power units in a maximum of 32 tokens. As Ferrari realized a loophole in the regulations in winter, FIA permitted the squads to carry on the development through the whole season. The deadline was, however, the season finale Abu Dhabi GP.
Ferrari had saved up four tokens for the last race as the team didn't consider their latest specification engine reliable enough in to be debuted at Austian for the American GP 4 weeks ago. Still, to make use of their in-season tokens, the Italian outfit had to hand in their final specification to FIA before the start of Sunday's season ending Abu Dhabi Grand Prix.
However, because they did not want their two drivers to be dropped back on the grid, they carry on using their previous engines, but they presented the final PU to the FIA.