Welcome! We've got a million threads, but this point on how to clean it: https://www.ecodieselram.com/forum/threads/cleaned-map-sensor-and-egr-tube-wow.1400/post-12151
At least they're aware they are failing and didn't say drive it.. that's a win.. sounds like you may have a decent, knowledgeable dealer. Keep us updated on how it turns out.
Tunes that go through certification that require extensive testing and data analysis. Kory has talked a lot about this on FB and making the investment to sell tuning legally. I don't know the process and requirements like he does... but, I do know some bigger companies are going this route now...
Over the years most people have said the intake doesn't really make a different anymore. Some say a little more sound is present, but other gains are minimal ( if any ).
If you buy you oil from the same place and have an account, they can likely pull the records. This is why it's always a good idea to get a maintenance tracking app so you can upload receipts.