Sure Isaac, the NA really never needs anything more than 270cc. Even with full bolt-on mods, it will never max out the stock injector. Swapping to an injector with a higher flow rate won't make any more power, it'll just make the car run richer and therefore worse. You'd have to also modify the ECU to compensate for it and then, at best, it would rune exactly the same as before. As for JECS, they made all injectors for the 300ZX, NA and TT, all years.

Hi Isaac, they are new and the price is accurate. The prices you mentioned are closer to what it costs to buy them through Nissan. This listing is to buy them from JECS, which is the manufacturer Nissan uses, so it's the same product, but less expensive since it's not Nissan-branded.