Did you recently install an aftermarket intake? Sometimes people get the gas tank vent hose mixed up with the hose that goes to the valve cover area and get them switched.
If not, the first thing to check would be your gas cap. If it wasn't put on securely it may giive throw a code. The simplest thing to do is to remove the gas cap, the put it on making sure it clicks a few times. Then reset your ECU by disconnecting the negative battery cable (black wire) for about 30 minutes. Then reconnect the cable and drive the car. If the CEL goes out and stays out, then that was the problem. If the light comes back on , then you need to proceed to further checking.
If you still have the stock airbox, look fot the hose that go into it at the bottom. There's one just under the inside lower edge near the filter that goes to the tank vent canister.
Check those things out and let us know what happened.