On the left is the s13 upper intake with secondary butterflies. On the right the s14 upper intake does not have these.
I am working on converting a 96 KA24DE to fit in a 93 240sx. Since I have to run the S13 intake on the 96, I’ve decided to try swapping the upper intake manifold. The secondary butterflies on the s13 intake is said to help low end torque but is restrictive on air flow. Perhaps a KA24DE-T is in order.