"Injector warning" should be renamed "injector, but more likely a dodgy connection in the plug" warning! I assume your ECU is actually giving a "dodgy injector" fault code? If so, read on.......
Injectors don't tend to "half work". Normally they either go or they don't. I would run a check on the wiring loom 'tween the ECU and the squirters, and pay close attention to the connectors. the fact you have managed a few hours running sounds like one or more might be shaking loose. (by disconnecting & reconnecting them when they were flushed has probably remade a dodgy connection in the plug(s), even just temporarily.
I don't know what kind of plugs (electrical on injectors, not spark!) the Opti uses, but if you can get inside and squeze the two halves of the electrical connection inside together a bit so it grips the pins on the injector better, it might make a more reliable connection. Then squirt some WD40 (or whatever your local brand of "save the universe" oil is
) to expel any dampness, and hopefully that should get you on the move again.
Good luck!
Also have trouble to reach the 5700 top rev the former owner said, only reach 5100... Very greatful to any ideas on how to go about this.
