how many bolts holt the plenum in place?

I'm sorry, hard to see in the exploded diagram how many bolts apply; it's quite detailed. I would suggest getting a copy of a shop manual illustration to assist. Definitely a bit of an involved operation.

Hello, There is an upper and lower plenum, each with 8 or 10 bolts. The spark plugs are located underneath the ignition coils, and there are none located underneath the plenum. Each coil is connected to one spark plug, there are three on each cylinder head for a total of six. What you are seeing under the plenum are the fuel injectors, and I don't recommend removing them as this is going to expose you to risk of vacuum leaks in the future.