I am in the process of swaping a JDM B20a into my 88 prelude Si. I was told that I would have to swap the distributor and intake manifold from my U.S. motor. I know that for emissions the intake would have to be swapped due to the EGR. Which I have no emisssions in my state so I am using the JDM intake anyway. But why does the distributor have to be changed?

You should check out honda-tech.com Lots of JDM info there.