Where are the mods to delete all the off topic bullshit in this thread?!?
For everyone who wants to understand the checksum, I wrote about it and have pictures from my car:
https://f30.bimmerpost.com/forums/sh...5&postcount=25
The simple answer is that piggyback systems (like JB4) do not change the ECU's tuning, so they will not impact the checksum. These will likely fail a visual inspection (which can be ignored) and may throw engine codes and/or prevent emissions readiness monitors tests from completing.
ECU flash tuning will pass the visual inspection. However, any changes to the ECU's code will fail the plug-in inspection. This cannot be overlooked by the tech since the smog computer is reading the VIN and transmitting it to the CA DMV.