Except I had all sorts of aftermarket parts in there from years of repairs, none of them with the all-important California CARB seal of approval on them, so even though it blew clean, it still "failed emissions" and I had to sell it to someone out of state. I'm still bitter about it.
Further, and most people don't know this is a thing, you CAN tune your car as much as you want and have it certified with all of those parts as a one off for about $5,000 and a six-ish month wait. This is how you can legally import overseas vehicles and get a California title and registration, but it's $5,000 per test, and it usually takes more than one if you aren't super prepared. After the certification the entire engine (including all modifications) are regarded as that being the SMOG compliant form.
One other major loophole is kit cars; SB100 allows for non-SMOG vehicles to be built as a kit. Not everyone's cup of tea, but you can build things like the Superlite GT-R [0] or SL-C [1] and never SMOG it.
You are barely correct. A filter alone is insufficient to be an issue, but a cold air intake will mean you don't pass smog in CA.
The parts may even be more efficient and less polluting, the government bureaucracy everyone here is worshipping doesn’t give a rats behind.