This my opportunity to share that in 2019 somewhere, which took effect in 2023 California told diesel vehicle owners that they would not be able to register or renew their vehicles if they did not meet CARB emissions board standards which were adjusted to a minimum of 2016 CARB standards (which are the most strict in the US). Which meant that your older vehicle was almost certainly not able to pass the emissions testing. If you didn't know, you can't just buy an egr, dpf, and scr system and slap it into your vehicle. Swapping in a 2016+ powertrain with a healthy emissions system into your 1996 pickup would set you back something like 25-35k not including the fab work. Point is, it's not practical and, in reality, what happened was that the state refused re-registration so owner I worked with are driving them without government approval, or had to sell them off an purchase new, expensive headaches.

Here is the exact bill. https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201920200SB210

CA is not the only state to flirt with these laws, working with the fed EPA to punish owners in some states. Id be happy to talk about CARB and cali's emissions standards. Virginia can force emissions tests and impound vehicles that police suspect have not been maintained or tampered, the can pull you over, and in some cases detain you.

You can spend your whole life running from the government, they will eventually come for you.