I replaced all my injectors in 6.6 duramax. after install my manifolds sound like they are running real hot. when I shut the truck off they make a cracking noise for about ten min.

 

Please post in the correct forum

 

Could be caused by fluids you may have spilled on the manifold, Could be corrosion on the the bolts and such breaking loose, could just be normal Might check the bolts and gaskets, The manifolds in what i consider a high corrosion area!
Just my opinion

 

could be even them contracting as they cool off