When I pulled the intake manifold off the other day I noticed a cover on the bottom. I removed the cover and there are four or five plugs underneath that cover. What are these plugs for? Also, how much does a person need to remove from the intake manifold for 58mm Throttle body to fit? What is a good brand for throttle bodies? Sorry for all the questions. I am trying to get a plan together so I can rebuild my engine. Thanks in advance.

 

The plugs were for machining the little holes you will see in the bottom of the intake ports.

 

To port the opening of the intake you should wait for the TB you select and then use the gasket as a template. There is no set "remove this much or that much" because some of the different TB have different port alignments, this is why I would wait untill you choose a TB then use the gasket.