I am speculating here but I would doubt that Nissan would have wanted to use the more expensive to produce 280Z in other markets as its creation was only due to the failure of the carb'd engine to safely meet Califonia's new emision limits and nowhere else in the world to my knowledge had those same emision constraints at that time.
As an aside the injection manifold and ignition system on the 280Z is pretty different to the injected L28 that we had here on the 280ZX's. I have the whole setup going spare if anybody wants it
That is hard to tell as it was only fitted because of problems at MOT time & 240 carbs were in short supply.
But as I was fitting injection I ported the head & had 20thou taken off then fitted a Janspeed manifold & exhaust & K&N filter & it was Quick!