Hi Joecar, I used basically the inverse of your equation in version 7.5 ( '{}' is the clue to version) and LS2's do not have GM.INJFLOW or an equivalent.
My attempt works with my new ride and displays correctly in version 8. Perhaps I am expecting too much but maybe one day version 8 will be the only one, or the only supported one.
Interestingly ECM.INJPDELTA, the effective fuel pressure between the fuel rail and manifold seems to be allowed for by the ECU and does not need to be included in the economy equation.

Cheers Steve