Be glad they were honest enough and just charged you $200. They could have said the EGR was bad and tried charging you for replacement. Move on.
If they were really honest they'd have fixed it without charge. Odds are they caused it and they know that, so do the right thing. From a business owner's standpoint, it ain't worth $200 to get on the bad side of a loyal customer. "You can't prove we did it" may not be the way you want to go.
Thanks for all the replies. At the least this thread has been entertaining and helpful. Makes sense to let this go. On the $200 being a lot of money, I'm trying to develop the habit of living without that 'cost plus' attitude and become cheap.
Does the service manual call for using loctite on the nuts? If so, and if they didn't, then that's probably why they came loose. I would politely go speak with the service manager and explain the situation. Going in half-cocked will get you nowhere. Being nice might get you a comped oil change next time you go in.
$200 is a lot of money to the dealership too. You asked for help, they fixed it and they charged you for it. Now you want a refund? Im not sure I understand that logic. I got a cavity after my dentist cleaned my teeth 6 months ago, no luck on my refund from the cleaning 6 months ago though We sold a car to a customer 2 weeks ago and he came back Monday with a cracked windshield and wanted us to replace it for free......I cant make this stuff up lol