For the P0455 I woould guess tighten the Fuel cap or make sure it seats properly on the filler neck. If this ckeck ok I would suggest to verify you're Vent control valve, she's located on the EVAP CANISTER. this valve gets always full of dirt and corrosion and fail open leaving a GROSS LEAK.
foe the oder two code mmmmm I would guess ure camshaft position sensor may be bad, this causing a desagree and induce a misfiring order. but inspect you're electric connections on these two part.