2014 Allroad shutting off while driving for a few seconds and then starts running again. Mechanic says it's a fuel tank vent valve. He says there is a retrofit for it and it will cost 2K to repair. Sounds fishy to me. What do you think.?

 

Does sound fishy. Have you checked for wet areas around the floor carpet or in front of the windshield under the hood? Sounds like a loose or a wet connection.

 

You should get the engine codes to see if it captured anything.