Strange noise

[Inspector_77]

Now that I have the CEL issue resolved I need to isolate an intermittent noise. It sounds like a heat shield rattling but only occurs when accelerating hard or between 47 to 53 mph (approximately). A visual inspection reveals that the timing belt dust cover is missing a lower retaining bolt and is cracked. I am going to replace the cover and bolt but wonder if the timing belt tensioner pulley could be making the noise? I am unable to duplicate the noise whilst parked and revving the motor.

Scott