I will also add...

Strict sequential injection also poses another challenge. Since with sequential injection you only have appx. 1/4 of the time to inject the fuel for a given cylinder, your injector capacity would need to be much larger to deal with the fuel requirements at full load/rpm. Big injectors fix this problem but make it harder to get a clean controlled idle. Since injectors have a minimum open time, there is a lower bound on the amount of fuel that can be injected - this may be more than you need to idle at 750 RPM.

A compromise would be to use a standard injector, run in sequential mode at low load/low RPM mode, and batch fired mode for high RPM/load conditions. (as someone mentioned, at high RPM there isn't much difference between between batch and sequential injection). I don't know if anyone is doing this hybrid approach or not, but I suspect newer cars would have it (as sequential injection does give better results with emissions) Does anyone know?

But when Volvo (read Bosch) was making decisions about injection back in the '80s, I suspect they wanted the simplicity of batch mode, and had no reason for the extra complications of sequentially fired injectors. Keep in mind that batch fired injectors, while not perfect, are light years ahead of carburetors in most respects.

-Steve