The VTEC solenoid and oil pressure switch are something that's not on the H23A1 so there's no connector for them in the harness but some Prelude (even some 92 even though there was no VTEC in 92 in America) are pre-wired for them already. But there's no need to worry for this now, that's on of the things you'll do last.

Next there's the exhaust gas recirculation (EGR) lift sensor. It's right above the EGR valve, the little thing between the throttle body and coil. Also the manifold absolute pressure (MAP) sensor is directly on the throttle body on the H22A4, on the H23A1 it's on the firewall behind the intake manifold. It's a little thing with a connector and 2 small rubber hoses into it. Don't forget to connect the speed sensor. There's also a ground around there.

After that, the next sensor is some sensor under the oil filter. You need a 7mm socket to get it out. Now comes the O2 sensor. Since it's on the header down-pipe, don't worry about it for now.

There are a few identical connectors here. First the knock sensor (that's the one above the oil filter), the connectors aren't the same on both engines, you might have 2 options here, one is to cut the connector a replace it with the one on the H22A4 harness, the other is to use the sensor on your H23A1. The next connector is going in the intake air bypass (IAB) control solenoid valve, that's the little black box under your intake manifold. And there's another connector at the end of the intake manifold behind the IAB control diaphragm.

We're almost done with the harness swapping, the rest of the connectors goes to the top or front of the engine. There's a connector alone that seem to be farther away from the others that goes to the resistor pack. The resistor pack is the little thing that's in the corner of your hood on the driver side near the windshield. It looks like a heatsink. Again here if you really want to use the injectors from your H22A4 you'll have to find a way to bypass that.

Now there's the wire cover that goes over the valve cover, you can't use the one from the H23A1 since the H22A4 valve cover isn't the same size. Just cut the tape at each end and unclip it and remove the wire from it. Connect the alternator, if you got an alternator with your new engine then you have 2 options, either use your old alternator or cut the connector on the H22A4 harness and replace the one on the H23A1 harness with it. Now put the new wire cover over the wire once you know how much wire length you need on each side of the engine.

Now connect the injectors. You can't put them in the wrong place. If you decided to use the new injectors you'll have to swap connectors with the other harness but since you all decided to use your old injectors cause they're bigger, that won't be a problem.

And finally connect the other connector that's on the intake manifold behind the fuel rail. And we're done with the harness swapping.

Last thing to swap is the 2 side mounts. On the 4th generation the mounts on the chassis are welled to the car, on the 5th generation they're bolted to it. Just swap the 2 side mounts and it'll fit right in as if it was made for it.