There are mixed opinions on this - some say that you can use fuel-rated o-rings that are the same size, and some not to. Apparently, the use a different compound for the upper and lower (the lower ones get warmer) and wanted them to last.
I don't see any trouble with using the "high-heat" o-rings on both ends of the injector, but I haven't done so yet (I've still got OEMR kits, I think.)
However, be sure of where your injector is leaking before you tear the fuel rail down. If it's an injector body leak, an o-ring job will NOT fix it, and you'll be wanting new injectors anyhow. Might as well do the job just once, it's really not that difficult.
And, if you've got one leaking, CHANGE THEM ALL. Chances are, the rest aren't far behind, and it's better to do a job once than several times. You'll spend the same amount of money by the time you're done, but end up wasting half a day with repeat work...
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