Any fix for the terrible noise when the started for the first time. THe exhaust rattles and sounds terrible for about 1 min or 2 but goes away once the pipes heat up.

 

are you running on stock exhaust?

 

I had a rattling a few months after I bought my car but it didnt go away when the pipes warmed. I got it fixed under warranty. It was a weld that had come lose in one of the mufflers.

 

https://www.myg37.com/forums/tsb-technical-bulletins/180963-tsb-rattle-in-main-muffler.html

Call your local dealership, explain the problem, give them the service bulletin number, and they should be able to schedule the installation of a new muffler under warranty. I called my dealership, took them a day to get one in, replaced my muffler the following day.