Today, on initial, cold startup, the engine made a distinctly different valve-train like tapping noise. It lasted 2 minutes while I pulled it out into the driveway and investigated, then it disappeared. Outside and water temperature were 45F. 2800 miles on the car. Hasn't happened previously. It's currently at the dealer, for them to check out tomorrow morning on first start. I expect tomorrow it will not do it, and I'll have nothing to report, but I wanted to get it documented and looked at.