It's a good idea to have the exhaust manifold and intake put together and milled as one piece... more often than not the exhaust manifold warps and it doesn't line up for seal once it's all taken apart for say..' a head gasket change' or something. If you don't mill it all together....at least leave it all loose as you put it together till you get all the nuts tightened to the Head side THEN torque down 3 long bolts through the top.
The engineers left some play in the those bolt holes on the intake iirr for alignment to the head.
