We just installed a fresh 4.6 romeo from engines direct .There is a loud clicking /tapping/grinding noise coming from the passenger side valve cover ,directly below the oil fill tube.from a distance of 6 feet it sounds like a diesel The engine runs ok ,but idle drops pretty low when you come to a stop . plugs are fine, pcv valve is new .Its not an exhaust leak .Im at a loss as to what it is .THe engine is under warranty ,but heck if i wanna pull it out and put another one in

 

It's a lash adjuster or rockerarm problem. Check with the company you bought it from to see if a field rep will come by and check it out.