Just an FYI from my smog guy
If they are using a CA standard OBDII test there were some changes put in place last Nov. (all shops due to update by 2020)
They can tell if the DME has been flashed by checking the CAL ID and/or drive cycle count.
They now count the amount of readiness tests and can check if they go automatically to "pass".
They also now monitor live data while the car is running and compare it to manufacturer supplied data to look for any variances.
If you live in a CA compliant state (I think there is 15 states now?) and you drive a 2001+ vehicle you get to swap everything back to stock every 2 years now
