fastiburon

M dealership service manager is removing HEAD in engine.

i've since about 1500 miles a loud clacking noise for about 3-4 minutes when i start the car every day.
now this noise is more loud then before.

starting the car i can ear it after 8-9 seconds in the 1000-1600 range, it continued decreasing
for 3-4 minutes and so disappear and everything is right.

this noise is enough udible in the head cilinder group: NOT FROM VALVE COVER ...
it isn't classic clicking from HLA that i eared in other tiburon.

i noticed that if i rev up engine rpm it disappear, when i release accelerator it compare!!!

dealer changed the cam metallic chain, the chain guide and checked hla with a spessor
between cam lobe and upper hla surface: he says it's all regular.

so he decided to remove head, he want check pistons and rings too
but i'm worried:
car has 9000 km (about 6000 miles)and removing head, oil pan, crank, connecting rods, and pistons... i think that they will find anything of anything.

what can i suggest to service manager?
checking valve guide? valve spring? retainers?
may a bad piston ring cause noise at start up?
or bad crank bearing?
may an ispective ( visual ) check up of components help dealership to understand the cause?

any opinion?
PS:
i used flushing oil but it doesn't help
i noticed that using mobil 1 5w50 increased noise.
i noticed that using thicker oils decrease noise a little.
i noticed that noise does not start immediatly after starting car: there is a little time lag before the noise compare.
and if oil level is about lower dipstick mark noise is less less loud !
it seems like noise is starting just when oil is circulating.
i think that one one bastard components is out of tolerance, when car is warmed it take his correct size!!!!!

help me with your opinions?
anyone experienced the same?

thanks all in advance