if he kept the obd0 injecters in the intake then yes you need that resister box in there.
otherwise if he put obd1 injecters in you need to cut and solder all 5 wires from the old resister box plug. 4 of thoses wires are your injecter 12+ power to each injecter. the other wire is the 12+ from the ign
without that the injecters wont fire

Make sure you have obd1s before you splice that plug together!