[Occasionally6]

Interesting to think about but I think there are a couple of considerations that make an F1 car different to a road vehicle.

They will have been operating, when on throttle, for much of the time at or near WOT anyway. We, in road cars, don't spend very much, if any time at WOT/full load.

When the driver doesn't want to accelerate there is still that benefit to be had by blowing air through the engine and directing it so that it generates down force via the body. If they can get the down force in that way they can back off the wings and find less drag along the straights. Any associated loss in engine efficiency (non optimum fuel and ignition) is offset by the reduced wing drag.

There is a most efficient ignition timing and air:fuel mixture for each engine, fuel and load. While it is possible to alter the power output solely through changing those things the efficiency with which fuel is turned into useful work reduces away from those optimum settings. Road cars operate under much lighter loads, with a wider range.

I do wonder if some (small) gain in reduced pressure drag might be achieve by directing the exhaust flow on a road car though.