Actually, you can legally pass with an open air filter as long as all of the sensors are in their stock location. CARB doesn't apply as long as the modifications are still being monitored by the OBD sensors in the stock locations. So a CAI will fail as they usually move the MAF and sensors, but an open air filter in the stock location will be fine.
I left my K&N on all three times I had my car smogged (at three different locations) with no problems at all.
