If you put an earlier incompatible 12A intake manifold or an aftermarket manifold that doesnt account for the center iron EGR port in the 81-85 12A Mazda Rx7, then this will accomodate you.

Block off the EGR port on 81-85 12A engines without tearing the motor apart to do so.

You will probably need some intake manifold gaskets and intake manifold o-rings as well.