The FIA intends to shut down a potential loophole with fuel flow. According to Racefans, at the FIA Technical Working Group meeting on Monday, the FIA believes that teams can increase the amount of fuel flow by using expandable hoses which would create extra storage allowing teams to break restrictions.
The current limit is at 105kg per race at a rate of 100kg/hour. This is measured by a specific meter. However, between the meter and the engine, the fuel flow doesn't get measured which might temp teams to use the expandable hoses.
The gains from this are very little, but any advantage in Formula 1 is worth doing, particularly by the top teams. Following the United States Grand Prix, Esteban Ocon and Kevin Magnussen were both disqualified for fuel related issues.