tapping, not tappets, help!
 

Can anyone suggest what might be going on in my engine; Its a 2005 2.8crd (diesel) voyager. We have had the engine opened twice now since a tapping noise started when accelerating. We assumed it was the tappets but its not, we have had some tiny washers replaced (i think they were on the bottom of the tappets - havent got the garage bill yet so not sure). I also asked the garage to check the manifold as someone said this could be vibrating, but this is secure. Or local mechanic is at a loss, can anyone help?
Heres hoping!