Sorry to see your problem continues. I mean, good lord it's just a car engine - you'd think a VW garage would be able to fix s VW, wouldn't you? So much for fancy diagnostics, huh.
This sort of thing kind of puts me off buying a new car. My Dad's MkIV had a simple problem which various VW 'technicians' and 'specialists' failed to diagnose, or wanted to spend literally £1000+ replacing one component at a time. In the end, I got a Haynes manual, talked to a few people on another forum, used my brain and fixed it myself, for nothing.
Before I put down any money on a new car, I'm going to see if the dealer will enter into a written agreement to replace the vehicle if found to be faulty.