Resistance. If the switch adds any resistance to the circuit then the voltage to the lights will be lower and so will the brightness.
If you have an ohm meter you can measure across the switch contacts and compare.
CA smog sticker part# ?
love the breakdown for part numbers but I didn't see anything about a part# for the California CARB sticker. The complete CAI kit comes with it. Anyone have know what it is or if it can be ordered separately?