There are many different options to nitrous control.
1. You can run a msd ignition module to control ignition retard
2. You can run a fuel management system that has nitrous control & or secondary fuel/timing maps. (neptune rtp, aem ems, hondata s200/s300 etc.)

To learn more about these systems you can check out the following urls:
Neptune: HRTuning
Hondata: Hondata - Honda ECU Modification and Enhancement
Aem: AEM
For more info on general obd1 honda ecu stuff, check out an efi writeup on phearable.net