ecu
 

I've tried searching but can't find an exact answer. I want to know if an s14 obd1 ecu will work in an s13 plug n play or will other things need to be swapped.

i'm pretty sure the pin outs on the wiring harness connectors are different between s13 and s14.

You CAN depin and repin everything to work, but that will take a lot of time.