I know certain 07 DMEs have been known to fail causing misfire issues. I don't know if that is what's happening here but you're getting no boost rather than misfires. It just seems impossible to have 0 boost and not be thtrowing a 30FF code.
Did he give you ANY codes that the car was throwing or explain how he came to that conclusion?
"I'm not surprised you get along well with all the other neighbours. If you put fifty children with Down's syndrome in a room there is going to be a lot of hugging." David Thorne