I'm always open to being surprised, but I'm just going to say it: I think the engine would probably still run reasonably well even with only two cylinders. Especially in your case, since cylinders 2 and 3 do not fire in direct succession.
When it was running briefly, did it run normally? Are you sure the injectors are compatible with the engine control unit? On eBay, things are sometimes sold by people who don't know what they're doing. You wouldn't want to have installed some cheap injectors from Alibaba that your control unit can't even control, would you? A link to these amazing things would also interest me

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