Here is my opening to my gas lid. The right side has a peg looking thing in it and the left side doesn't. Other than that it looks normal. I keep getting a PO442 and PO455 code (small and large leak) I've read and most say it's a loose gas cap or the gas cap isn't sealing good. I purchased an OEM cap and it fits tight. Just curious if there's supposed to be a hole to the left side of the filler hole. Thanks!

 

My '06 MCS looks the same. One hole, one plastic plug looking thing.

 

Could use a little cleaning, maybe. Gas cap is $3 to replace, so I'd start there, also take a look at the charcoal canister threads, the can ethier become cracked by a well placed rock or suspension travel over a pothole, or saturated by gasoline from the tank being topped off after the auto shut off or again hitting a pothole and having the fuel slosh up there and saturate it. The canister runs about $375 but some have managed to reseal cracked ones.