That's why I got a car that was already fucked up. Momma didn't raise no foo.

Maybe you're leaning out in that last 500 RPM. They always run best just before they blow up. And let me be the first to verify that fact.

You are correct about the Injector offset vs batt voltage...

Definition: The delay beteween when the injector driver fires and when the injector actually starts to open.

If this value is too low, the actual pw will be slightly shorter than commanded across the board and you'll run slightly lean. If it is too long, it effectively increases the pw and you'll be slightly rich. The offset varies with battery voltage because at lower voltages the injectors take longer to respond.

The EEC uses this to compensate for the injector open and close time. The amount of time it takes the injector to open and close varies by the amount of voltage available to drive the injector.

The offset vs batt voltage should be good for most injectors, but if you want to adjust it then use the original injector size / new injector size ratio.
19.64 / 42.1 = ~0.45 now multiply the Y value of the batt offset function by 0.45.......