general problems of the 2004 Mercedes Benz ML350

Hello my check engine light is on in my 2004 mercedes Ml350 so I took it to a mercedes dealership for inspection and repairs. They kept my SUV for 8 days and finally called me back and said they believe the check engine light is on because I need to replace my charcoal canister shut off valve. Now this component takes the gas vapors that has not been burned off and reroutes it through the charcoal canister and back into the engine so it can be burnt off and not enter the atmosphere and enter the inside of the vehicle. Well my SUV has failed inspection for emissions and that’s why I brought it in to mercedes. Well the service department at mercedes called me 8 days later and said mercedes does not make that part anymore. And no other aftermarket company makes it either. They charged me $200 to tell me they can’t fix it because the part is not made anymore. So am I safe ? why mercedes never recalled a vehicle that can not pass states emissions test. I wrote a letter to the head of mercedes in europe and the united states. They offered me $2,000 off of a new mercedes or $1,000 off a pre owned mercedes. Sounds like they know something is not right here. So my complaint is can a car manufacturer stop producing a part that is needed to safely pass the emissions test and isn’t these fumes harmful to me and my family?.