Ferrari followed the rules to the letter, if not the actual spirit of the rules. Some talk of the fuel flow meter taking measurements at specific times, Ferrari found out the timings and were able to adjust their timing and flow to be within the rules when measurements were taken but push more fuel in between these times. Considering the revs that F1 engines run at, even having a few extra piston cycles with extra fuel would be an advantage. Ferrari were well up on power halfway through the season and were then suddenly slower than before again.