FIA issues a clarification that's anything but.
How is it possible to interfere with any mandatory device in any way at all? Surely it's a sealed unit and off limits to teams?
My understanding is that the fuel flow meter was not tampered with, but a cunning method of fuel pressure 'pulsation' was alleged to have skewed the meter reading.
In the same way as any fuel injection system can track fuel used by knowing the injector flow, fuel pressure and duration. The engine ECU does some big sums and this is how we read fuel consumption on our dashboards.
I believe the FIA fuel flow meter samples the pressure every few milliseconds to gain a flow rate over a known orifice.
If however, the pressure is cleverly 'pulsed' between the phases of the sampling rate it may be possible to flow more fuel without detection. More pressure equals more fuel flow.
This is all theoretically possible using an electronic pressure relief valve already part of the engine control system, but proving this was 'beyond doubt' used to 'confuse' the FIA meter and not just give the engine injection system what it requires, is indeed, a complex area.
But, it certainly would not be the work of a moment to get it to work! Equally, it is very unlikely that there would have been a 'natural' resonance in the fuel pressure to phase align with the FIA fuel flow meter samples.
This just what I have managed to glean from talking to people closer to the 'coalface' but it may well be far more complex than my simplified overview.