I would run the oem tune just in case they decide to use the equipment they use in CA. I heard rumors they were looking for tunes, but nobody I knew had been caught, and even my smog guy said he'd never caught anyone. That was until I showed up... See pix.
Can't help with what is up, but I can tell you how I can get my monitors to clear instantly, and imo you should do the same for future use. This is also how I got mine to pass smog, btw. Tuning is a bit risky, but a lot more so with a Mercedes using HP Tuners. The reason is you have to load a patch for HP to work, and sometimes that will brick the ECU. If you're not prepared you're looking at thousands and likely weeks before your car runs again.
So before I did anything I bought a KESS unit on aliexpress, which cost ~$60. With that you can make a copy of the data on the ECU, including all the secret security stuff. If the ECU bricks you can try loading that back on. If that fails you can load it onto a junkyard ECU and off you go. I bought a junkyard ECU anyway, just to play with, which cost me $200.
Back to the smog and monitors: When I copied the data, the car had no codes and all monitors cleared. So after my fails at smog time, most of which were codes, it dawned on me that I had that clean copy. So I loaded it and instantly I had no codes and monitors are cleared! Fyi
So even if you don't need a spare ECU, you may find yourself in need of a clean ECU.
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