Exhaust components necessary?

How important are these two items: manifold insulator - and the heat shield/insulation on the front pipe? The pipe I’m talking about connects directly to the pre-cat which is connected to the exhaust manifold.

They are there for a reason. The manufacturer wouldn’t have just added them for kicks.

There are a couple of reasons why the exhaust is shielded/insulated between the head and the catalytic converter. First, it is really hot and can damage nearby plastic components such as anything electrical. They may also be near brake lines. The second reason is that in order to work, the catalyst has to be hot, and they want the catalyst to heat up as quickly as possible after you start the car. The exhaust is insulated to keep it from loosing heat that the catalyst needs.