i found some more info...i think is easier than what i thought before..what my friend said....as for engine bay wire harness you dont really need to buy a gsr OBD II harness.....our 92-95 civic OBD1 engine bay harness will plug into the 99 si OBD2 engine harness...
BUT all you have to do is run a few wires from your 99 si engine to the ecu (a jumper still need if you still want to run the 99 si ECU or u can opt that for a OBD1 p30 ecu or p61 ecu) and that should work......here a links i found that will clarify it.....thanks to the man KATMAN (FF-SQuad)..
http://www.jdmhondaparts.com/ecu/wiring/
http://www.jdmhondaparts.com/ecu/wir...1harness_1.jpg
