I have a 1996 ek hatchback with complete em1 harness for dash harness and engine. My issue is the plug to connect rear tailight harness doesn't match up and before I start soldering anything I wanted to know it will work and the hb lights will wok properly with the si harness from 1999.

 

obd2a and obd2b didn't know rear lights etc had a different plug between obd1A/B. I think you'd be ok as long as you match wire for wire.