I have a 02 F-150 with the 5.4 and have a clicking noise only under acceration that sounds like it's coming from behind the dash area of the engine compartment or by the pedals. I thought I had a bad exhaust manifold so I put on headers and now it seems like it's almost worse. I don't see anywhere were there would be a exhaust leak. I also only get 13mpg driving it nice...Thanks

 

Check your spark plugs it sounds like one might be getting ready to launch!!

 

I just got done replacing the plugs...they all looked good, none were loose.