Before i start, i have searched. for hours. just cant figure it out!! I have a 1990 integra with a 97 jdm gsr and currently is converted from stock obd0 to obd2a (i think its obd2a.. its obd2 something). i want to convert to obd1 and have purchased the following:

obd0-obd1 jumper harness
obd1 p72
hondata s100
greddy 4-2-1 header with modified 2.5" collector
carsound 53006 hi flow cat 2.5" in/out let
ran custom 2.5" piping back to a greddy sp2 muffler

I have the primary 02 sensor on the header and no o2 sensor/o2 bung was needed on the hi flow cat for obd1 so i purchased one with out it (zip tied the second o2 under the car)

My main question is do i need an obd1 distributor, alternator and injectors? And i have also hear about some 4 wire thing for the o2, im a little confused

 

The OBD2 distributor will work fine with the OBD1 electronics, you will just have to change the connector to match your engine harness.

The OBD2 alternator will work fine as well, again just change the plug on your engine harness to fit the alternator.

If you are running a stock/unchipped P72 ECU, you will need to wire the additional three wires to the O2 sensor. (if you've purchased a decent quality jumper harness, these pigtails should already be there and just need to be run to your O2 sensor)

If you are still running an injector resistor box on your DA, you need to either install the DA integra injectors onto the GSR engine, or remove the injector box and use the GSR's injectors. (Either way the pins at the ECU for each injector should see around 12 ohms resistance)

 

+1 on what he said. Also remember, if you are running the USDM P72 ecu, your JDM ITR motor does not have a vtec pressure switch. You can jumper the Vtec solenoid wire and Vtec pressure switch wire together to eliminate the Vtec pressure switch code.