2012 ECO, AT, 86k miles, well maintained. 1K miles ago my engine started whistling immediately after starting cold, then as engine rpm's come down to normal (800 or so) the whistling stops. I can't pinpoint location but seems to be from behind or below the aluminum heat shield over exhaust manifold. Any ideas you smart Chevy Cruze folks? No codes, smooth idle, no whistling while driving. There is also an increase in the exhaust fumes in same area, almost like exhaust is leaking. I can feel a slight breeze same location. ????? Thanks.