I seems to recall that the fuel consumption gauge is vacuum driven? Not smart enough to know what that might mean when it comes to your problem and it being pegged at idle. Doesn’t seem right though.

Try unplugging the SAP and driving it for a while to see if fuel consumption is affected. It will pop a code, and likely the SES light too. When working properly, the pump shouldn’t run for more than a few minutes on cold start, and only at colder ambient temps. You may also need to unplug the vacuum control switch that sits on top of the motor that opens the SAP valve to allow the air into the heads. That valve should stay shut too for a proper test.

Also, I think my foxwell has SAP text functions and live data. You could both test it, and see if it is in fact running when it shouldn’t be.

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee