Sounds like you're looking for the injector dead time dialog?
Go to "fuel settings", then "Injector Dead-time/PWM".
Be warned though, this one's quite a bit more complicated than previous MS versions. I don't have experience with MS1 but it sounds like it's like MS2 where there's just a single "battery voltage correction" number (in ms/v). Because the correction tends to be nonlinear, in MS3 it's not a single number any more, it's a table. You can read the documentation on it here: http://www.msextra.com/doc/ms3/fuel.html#deadtime