Mud, just went through something similar. This might be helpful. My smog guy is a star station. He has been smoging our vehicles for years. Two part smog certification under new Ca 2017 rules.
1. Check for any modification or change of factory parts. Any modification/change must be CARB approved and have CARB cert number sticker. Cert number must be checked to insure that mod/change part is application specific to that vehicle as equipped. If step 1 fails, stop smog cert. Tell owner to correct.
2. New State software now checks the EPM, EMS etc for out of spec data. Can not tell you exactly how that works. But it is pretty sophisticated.
Having said all that. I have seen over the years smog legal vehicles that they pass that are modified. So changes, upgrades can be made if approved.
When I replaced the factory CAI on my 03 1500 5.7. I took the CARB number that the manufacture provided to verify that it was still CARB approved.
When I replaced the factory valve covers on my Grand National. Had to show that I did not modify or change any factory smog parts. Since my tech did not know what he should be looking for, he asked me to bring down the factory valve covers to confirm.
My ****** exhaust is not CARB legal "today" Because it was legal back in 2004 and the vehicle has passed every year since, we are gtg.