I have a 1993 GS 300 Lexus and I noticed gas leaking from the charcoal filter's Vent tank which is directly underneath it. I lost approximately 1/4 tank of gas, so I disconnected the bottom hose of the charcoal filter and put a rubber plug on it until I can figue out why I'm loosing so much gas. I chased down the hoses and they are all connected. Could it be the Could it be the check valve?