Unfortunately without seeing the car and driving it myself, I won't be able to tell off the top of my head.
Even if they do make stuff up, guess what, they can't charge you for anything as you have full warranty on engine and parts.
I'd suggest, you take it to them, have the Service Manager sit in the car and drive with you. Point out what you feel is wrong. I usually take a micro-tape recorder and record the conversation.
The agency does not want to get a bad name. If they try to cheat you, you can always write a letter to Mercedes Headquarters. I once got full money refunded on a 1997 Mercedes Benz Transmission that went out suddenly after 6 yrs even after the warranty expired directly from headquarters because I had proof that the agency was lying and trying to cheat me.