Yes you will have bad fuel consumption.

Doesnt make much difference when under load though.

Usually batch injection triggers the injectors EVERY crank cycle if all 4 are
fired together or in alternate revolutions if triggered in pairs.

If you get the wrong pair in the wrong cycle that too can cause fuel drop out and cause high fuel consumption and bad idle.

Best use sequential (may need to double pulse width depending on configuation and ecu type etc...)

You will however need a phase/cam sensor so the ecu knows which
cycle the engine is on to do this properly.
(or some trick software )

Another issue when using EITHER modes is injector PHASING.

I.E WHEN the injector actually starts to open with respect to valve/crank position.
Large injectors will only be at there best is PHASED correctly.