Boom: if the filter is paper, blow it out or use a stiff paintbrush to clean it. But look closely - if it is fabric, and oiled, most good parts supply houses should carry a K&N filter cleaning kit, consisting of a solvent to soak the filter in. Then you rinse it off with a hose, let it dry, and there is spray oil in the kit that you reapply to it.
You don't need the little black hose - it's pointing air in the right direction anyway.
The CEL mentioning "evaporator" seems to be pointing to the fuel system, which can have a fume-purge system. However the A/C also contains an evaporator, so that single word doesn't help much. Try this: turn your ignition key OFF-ON-OFF-ON-OFF-ON (without cranking the starter), then leave it on with the car not running. After a few seconds, the idiot lights should all go off, and either the CEL will blink in code, or it will flash numbers in the digital odometer. Your Lexus owners' web ring should be able to provide some info on what that code means. I don't know for sure if your car will do this, but many do.
Good luck!