After the DT header installed, I have some funny "Metal" noise.

[2garfields]

Usually happens when it first start up, it would have a single or muti "Medal' Click nosie, then it would disappear. Sometime it is very minor, but once in awhile, it is very loud.

Anyone has any similar experience, it happens right after the shop installed the DT header.

 

[Trunk Monkey]

Video it and post it. What you've posted is pretty vague.

 

[Layonnn]

Might have a nut loose on a stud that hold the header on that is creating an air leak, then as the header/block heats up and expands it closes the leak.

But yes a video clip with good audio would be best.