I got a rx7 1987 N/A with a N326 ECU so can I use an engine harness from a rx7 1988 N/A ?

 

I am pretty sure you can. S4 Is 86 -88

 

Well I read on frequently ask Q that 88 use a N327 so its the same conector for the N326? But it has logic to your answer

 

It depends on your injectors and if they are the same.
the 87.5-88 models use NO resistor pack and a HI impedance injector..where as the 86-87.5 used a Resistor pack and LO impedance injectors,
The injector connectors are NOT the same and you can tell the LO's have a center notch and the HI's are offset connector,(see the FAQ thread for Sec GEN.).

You can use the harness BUT also use the injectors it came with.That way you do not have to rig the harness for resistors or bypass the resistor pack(depending on which direction you go).
If you use the LO impedance harness then use the LO Impedance injectors AND the Resistor pack.