I find it funny that you think Kubota has anything to do with this website, it is privately owned website.
You seem awful angry and yes, some posters are not as kind as others, but the information being provided is consistent. I'm sure you have posted on other forums and realize you have a wide variety of posters with very different personalities and communication skills.
With all that being said, multiple people have come to the same conclusion about your situation.
- You have the dreaded 3350; this engine is known for DPF issues so much so Kubota has discontinued it and offers lifetime coverage on the DPF system
- There are WSM out there that cover your tractor and show the electric system; the part you are looking for is not on the schematics because it isn't a factor item
- The part you took a picture of is a device that is illegal to use in the US; the opening page makes it sound like a nice device to help reduce errors, yet when you read further, the device is designed to defeat the DPF
- Whomever put the device on there, has most likely negated any warranty claim you have on the tractor (full disclosure, not a lawyer, I did sleep at a Holiday Inn)
What you will find, if you hang around long enough, there are a lot of good, knowledgeable people on this forum with a wide array of knowledge that can help with many issues. Yet, as with all forums and in real life, we all communicate a little differently and you take the roughness with good, but you can get the answers you need.
Sadly, I think in this case the answer isn't what you are wanting to hear.