this has nothing to do with obd wiring, that motor is the correct obd for your car.

So you have a DX.

Dx means no vtec wiring from the factory. You need to add 2 wires if I remember correctly.

The vtec solinoid goes to pin A4 on your ecu, I'll show you how later I'm heading to the gym right now.

The vtec oil pressure goes to D6.

I don't think the p28 has knock so no need to worry about wiring a knock sensor.