There is a vent for the tank, yours might be kinked. You will have to lift the tank. There is one allen head bolt holding the rear of the tank, remove the bolt and you can slip the tank back and lift the rear of the tank 4" or more. Prop the tank up and look to the bottom front of the tank. There are actually two rubber lines coming from the arch of the tank. Follow each from the tank down to where they terminate. The vent plugs into an evap canister. Your problem could be between the tank and the evap or where the evap goes into the air box. These rubber hoses are pretty soft and easily kinked. The vent easily pulls off a metal spigot on the tank so you can check that for a clear passage...just blow into the hose.
Peter Y.
