Is the b18b intake manifold a direct swap on the b18a or is there modifications/parts required on a b18a to get this to work correctly. Oh and this is for my buddies 91 Integra by the way.

Yes I think ti is a fairly straight foward swap. There maybe some sensor relocating but that should be it no custom wioork to be done.
I have 3 of them you want one? Pm me an offer if you want one