Ultimately, there is going to be some risk. Generally, most cops don't worry/care/know about illegal engine mods. For the most part,they won't enforce such things if they don't have heavy suspicion and/or you're doing something really stupid (illegal street racing actually have undercover cops who are pretty knowledgeable relaying info to uniformed officers). Not sure how prolific this still is as my knowledge of it stems from aspects of insurance fraud they were dealing with when I was an adjuster and I've been out of the industry for 6 years. The program was growing at that time and they were pretty knowledgeable about the 240sx and the SR20 motors being put in them.
I have heard of limited cases of non-CARB turbo cars being caught on regular streets. They were rare, but there is still risk.
alms24sebring wrote:Cali laws are another reason why it just needs to drift off in the middle of the Pacific, but rules are rules.
Aftermarket manufacturers can build turbo and supercharger systems that can be CARB approved and therefore street legal. While its ultimately a problem for enthusiasts, understand that the intent is to prevent the huge increases in emissions levels (which could be on the order of hundreds or thousand times greater than stock) that come with adding parts like turbos, superchargers, intakes and headers that might undo some of the progress made by CA emissions standards. It basically puts the parts through similar standards as the OEs. There are some procedures in place to allow an engine swap from the same or newer year legally as well (must be a motor approved for use in US, i.e. no RWD SR20 motors).
Now, I understand the reason for the animosity towards CA on emissions, but there are very good reasons for the laws to exist. And if there were an easier way to ensure modifications meet or exceed OE emissions, I'm open to it. The standard biennial smog check is very limited compared to what manufacturers actually test for.