since the car was DPFI, it doesn't have wiring in the cabin harness going to the firewall for the extra 2 injectors nor the 2 wires for the Cylinder Sensor in the distributor - this is the wiring that needs to be added to your DPFI engine harness to convert it from DPFI to MPFI - you will need to do this regardless of whether you run it OBD0 or OBD1 - once you have done that, you will have the necessary wiring and can use the OBD0 PM6 ECU from the 88-91 Si along with OBD0 distributor - going to OBD1 will require that you purchase the OBD0 to OBD1 jumper harness that allows you to plug the cabin wiring harness into the OBD1 ECU and you would need to wire up the 4 wire O2 sensor - if this was a VTEC engine, then i would strongly recommend converting it to OBD1, but since it is non-VTEC, then OBD0 will work fine - as long as you use the OBD1 injectors from the B7, you won't need an injector resistor box - pretty simple to stay OBD0