if it has the 91 si motor you have a d16a6. The closest factory obd1 ecu that will work for you is the p06. Use a factory 92-95 civic dx or lx wiring harness, and the p06 ecu. It's not gonna run perfect but it'll run pretty good. You could also use the actual obd0 1991 civic SI computer but that would require an obd1-obd0 wiring harness.