OK - now that I see you have used the Z32 unit on your S13 I have another suggestion!
Having just done this conversion on the RB25DET in my 200ZR I found on initial start up that there was a misfire and inability to rev - like a bad MAF. I split the loom to check that the wiring was correct and found that the engine ran fine with the loom spread! The problem seems to be that where the loom splice was made, the shielding around the signal wire was open allowing interference from nearby electrical signals. Taped it up, added a layer of tinfoil at the join, taped it up again - problem solved...
So - check the continuity of shielding around your signal wire at the splice...