So I bought this 97 civic that had a d15b7 swap. Now don't ask me why but for some reason that guy who did it put everything from the d16 on this d15(including the ecu). So I swapped the edu but now it has a crappy idle that jumps from about 500 to 1500. Now I noticed more noise from the air intake, which I believe is because it isn't running rich anymore. But could my problem be because the intake on it is too restrictive? I plan on replacing it with the right one anyways but I wanted to know if it will make a difference.

 

No, the D16 intake manifolds are not more restrictive than the D15 intake manifolds. If you're having a pulsing idle, you need to check for vacuum leaks, and clean your IACV. Is the CEL on?

 

with the new ecu the cel is not on

 

but where is the iacv on the engine?

 

On the back side of the intake manifold.

 

of the d16 manifold or d15 manifold?

 

I have a d16y8 intake, yours may have one. If so it's located near the fire wall right next to the TB. Looks like a small cylinder. Coolant cycles through it so make sure your cooling system is completely bled. Also check for leaks which may create air pockets.
If you still have the same issue try tapping on the cylinder of the IACV while it's acting up with a screwdriver handle to see if it changes your idle. If so I would look into cleaning or replacing the valve