Well that sucks. Sorry to hear of the mis-diagnosis, which is what this has become. A repair is only as good as the tech's efforts. Request the shop foreman to get involved with the situation and meet with him, he is your best contact. The service manager has a lot on his plate and typically allows the foreman to directly supervise repairs without being micro-managed. Your salesman is the wrong person to go to at this point. The service advisor is a little better choice but he will have no authority over the techs, he is more a meet/greet/service salesman. Some techs are better than others mechanically, some techs care more than others and unfortunately you as a customer cannot tell which is which but the shop foreman does. Some shops will allow you to speak to the tech, if so maintain courtesy and understanding. This face-to-face helps personalize the experience and both parties benefit. Rechecks receive priority in any well run shop and loaners typically are given priority as the dealer is rated/bonused for satisfied service repairs and penalized for not. Last thing a manufacturer wants is poor service, buybacks, lawsuits. I've seen techs get locked out of being assigned additional cars (where they make money) until their recheck is repaired and QC'd by the shop foreman. Benefit of a doubt should be given to the tech and he also should seek the shop foreman's assistance. Sometimes a tech tries but misses the root cause. 30 plus years working at GM service department for a large dealership, I've seen some bad and good folks. Hopeful your experience improves.