I want to add that I am not current on all new technologies. When I worked in a pump and injector shop and a Deere dealership - there was no known way to "rebuild" a pencil injector. So, I do not know what is being done to the pencil injectors sold now as "rebuilt."
I DO know this. The meaning of the word "rebuilt" has been messed around with a bit by many sellers.
I see it this way. To "rebuild" anything is to return it back to it's original projected service life it had when brand new.
When we "rebuild" an engine - we renew all moving parts subject to wear and movement. Cylinder walls, pistons, rings, bearings, valves, valve guides, seals, oil pump etc.
But . . many pump shops sell injection pumps as "rebuilt" when often - major moving metal parts are NOT renewed in any way and sometimes have near 1,000,000 miles on them or 25,000 hours of use. They get resealed, recalibrated and often just minor new small parts installed.
With fuel injectors? We used to clean some up and recalibrate and sell as "good used", "used and checked" or maybe "reconditioned." We never had the nerve to call any injector "rebuilt" unless it actually had a brand new nozzle assembly installed. There IS no such thing for a pencil injector. But to be fair - maybe somebody has come up with a way to remachine them and renew their service life. If so - I'd like to hear more about it. A process might exist but I've yet to see any evidence. When I ask sellers - I often get an angry response like I got from Lavoy from JD Crawlers.
Considering there are brand new pencil injectors available for Case and Deere and Oliver for less then $30 each -it seems to me that high dollar attempts to "rebuild" would not be cost effective.