So I'm a little confused, and wasn't sure what to search.

If I plan on buying an aftermarket Intake Manifold/Header with a larger bore, would I have to buy a new throttle body to match the bore?

Another question. I have a y7 engine, I planned on swapping my manifold for a y8 manifold. Will there be a diff at all. I noticed the bores are the same.

ONE more question. I know neither will give me much of a gain at all by themselves, but which would give better results. And aftermarket header? or an aftermarket throttle body? I plan on getting both in due time.