Welcome! Just drive it and enjoy it. The rattle isn't going to do any damage nor is the momentary high idle. If there was a problem we'd all have new engines after a failure.I have a 2010 crewcab,le with some of the issues and concerns that I have read about on this forum.(cold start engine rattle,high idle speed on cold start and passenger seat back shake.)But for some reason, I'm liking this truck more everyday?