Screw CARB. I live in Kommifornia and hear about this crap all the time. They change the rules and promulgations constantly so that there isn't any way at all to know what the current thinking is. It's best to ignore the whole noisy mess. As a private non-commercial, not-for-hire, recreational vehicle they don't have any real authority over me or anyone else with a private Motor Home. They just think they do and try to scare us into complying with their Diktats. They have to locate and catch us first, and they admit they have bigger fish to fry anyway so they leave us alone.
Why would you ever choose to willingly place yourself under their authority just to "Be Legal". They are the Usurpers and "We The People" should not comply with unconstitutional "Laws". Just because they say some Regulatory issuance is the Law doesn't make it so, unless and until the Legislature takes it up, and even then there are many grounds for disallowing such Executive/Legislative Branch overreach. Oh, and first they have to catch you, and who's to say how many miles you have been in Kommifornia anyway. "I have no idea, why do you need to know anyway?" works if actually stopped. Being from out of State means you don't have any obligation to inform them of your unknown future travel plans. Do you do this with all the other 49 States you may decide to traverse someday??? You also don't need to go through Scales or POE's either, you're a private vehicle.
You are an American Citizen with a God given right to free and unfettered travel anywhere in these United States with no interference from any over-reaching out of control Government entities. Remember this, and choose to be ungovernable, and don't give them any more power over you in this regard. Your State of Residence has your legal qualifications already met and any other State is obligated under the Constitution to honor whatever your State requires, DLicense, insurance, registration, etc.. Kommifornia can go suck eggs trying to extort from itinerant travelers passing through the State. You owe them exactly NOTHING. Don't give'm anything, it only encourages them to do more horrible things. Rant Off.