2010 F150 FX4, approximately 180k miles. I had the emissions done a few weeks ago, and when I left the shop, the truck started making noise. I'm not sure if they are related, but it might be relevant info. The truck makes a rattling noise exactly at 1k rpm with slight acceleration. Under 1k and over 1k does not make the noise. Also coasting at 1k rpm does not make the noise. A few other threads have suggested the heat shield. Does anybody have any other ideas?

 

How about you check the heat shield and if so fix it . If not ,you might ask the shop what they disturbed that could cause that.