S13 intake manifold on a S14 KA
 

Is there a any pros to this mod cuz i have seen this on an S14?..or are they just the same as the S14?

i am pretty sure they are the same physically but the electronics are different mainly the lower plenum, throttle body is the same

You talking about the lower intake manifold or the upper plenum? If you're talking about the upper plenum where it meets the head, the S13 DOHC has intake butterflies. The S14 DOHC upper plenum does not and it allows the air to flow more freely. If you're talking about the lower manifold that mounts to the TB, they're slightly different.

If the car is OBD-II, the TB ARE NOT the same.