You will be required to show the DMV agent the Meets CA emissions sticker or 50 state compliant sticker whichever it has. If its been removed all bets are off. I went thru a PITA bringing in a KTM 950 from AZ because I couldent find this sticker even when the KTM manual stated ALL 2005 KTM bikes are 50 state compliant. They will check the Vin#s and look at the engine numbers and frame numbers to verify against the title and to issue a Ca title. Far as the exhaust they never asked, looked, started it or seemed to care about mods.
Reality is merely an illusion, albeit a very persistent one.