If you have spent $4000 + out of pocket, ask the service manager when the next time his area rep will be in, and ask to speak with them both. I would also recomend an attorney at this time. You should deffinately not have to pay another penny, and if the dealer is not able to fix the car, they need to find the people whio can. Unfortunately this is probably a MB dealer. (I'm a x-fire tech saying this) The tech should only be fairly compensated for diagnostic time, however, not the full amount since he hasn't gotten right yet, and no time for repairs performed, since it hasn't been fixed.

P.M. me with any availible codes and attempted repairs, and I will see what I can come up with. I also re-emphasize, get an attorney.