didn't see anyone talk much about injectors
they have high pressure going to them, or it could be high pressure or it could be "low" depends on what the ecu wants
inside the injector is sort of a relief. If rail pressure commanded it 30,000 psi and the injector "relief" is stuck open, it won't build 30,000 psi and bypasses fuel, and you get a low rail pressure code. Very common on Duramax engines, and I did quite a few kubota's too when I did tech work-mostly on the L01's but occasionally an M.
if rail pressure was ever really high for whatever reason the rail pressure sensor gets damaged. Replace the rail is the only way to fix this. If the rail pressure sensor is damaged it will show erratic pressure readings, or sometimes no reading at all or sometimes it'll just show high all the time. A failed rail pressure sensor can also damage the supply pump assembly and sometimes the scv. many techs have replaced the pump when they get a low pressure situation but ignored the injectors and RPS, and even more common is the ignorance of the rest of the system. If the system was full of water, the liklihood of damaged injectors, RPS, SCV, lines, pipes, supply pump, and possibly other stuff is high. Water in these common rail engines gets very very expensive, quickly. I would be surprised if a fuel rail assembly, injectors, supply pump (just those 3 parts) don't add up to around $5000.
if injectors are suspect pull them out and send them off for testing. even if not suspect, if there's been water in the system, pull em and send em out anyway. As said make note of which injector came out of which cylinder so they can go back in. If they have to be replaced, the software and hardware is required in order for the engine to run. properly. Dealer only. the injectors have a number on them that must be programmed into the ecu
and on the part number arguement, yeah that last digit is almost always a supercession. It may be that Kubota's supplier has changed it, but they haven't updated kpad yet and thus the dealer knows nothing about it. It wouldn't be the first time I've seen it. Parts guys no matter what dealer they're at, don't know everything, no matter how good you (or they) think they are. BTDT. And I might be wrong. I ain't perfect either.