Mayby i'm wrong at this, but after messing with Megasquirt for a couple of months, i learned that low imp spi injector is a peak&hold type, so spi ECU is programmed to treat it this way. It needs a high pulse to open and then current is lowered for the rest of the pulsewidth.
Mpi injectors are high impedance and need a steady voltage for the whole pulsewidth, so driving them with the spi ECU might mess things, as it will limit current after pulse start and injectors might shut before end of pulse.
Mayby that is why my attempt to remap the spi ECU, so it works with 1242mpi setup, failed. When we tried to lower the pulse below a certain point, so we reach stoichiometric, injectors were suddenly shutting and car stalled. It was either rich or stalled.
Perhaps Oldschool changed injector driving code, not only maps?
Although, car runs fine on an unlocked 1242mpi ECU (8F.5T), using modified stock harness.
