I'm in the process of cleaning-rebuilding a 95 LT1, This morning I removed the sheet metal cover on the bottom of the intake manifold to clean the "Gunk" off it so it won't get in my nice clean engine. What are the large pipe plugs in the manifolds purpose and do I need to remove them to properly clean the manifold? I thought I was OCD until I realized the letters weren't in order....

 

I think the holes were there for the casting process and then threaded and plugged. I don't think it's necessary to go that far, but that's just my opinion.

 

I think you are correct. I would hate to get one stuck and mess up the threads and compromise the integrity of the manifold. Got more plugs than a block!! Must be a really involved casting process..Thanks