rattling noise under or in engine when car is cold or first started? driving or setting still(idling).

Check heat shields on exhaust to make sure they are not loose

repaired all exhaust parts and shields noise still there.

Just to add to this one have you checked the upper engine mount by the valve cover to see if its colasped or torn?Its really common for them to do that.Thats the first thing i would check.Let mw know what you find.