Here are the steps for wiring the BP to the Festiva harness, this is only if you have a fuel injected car:

Injector Wire Harness
You need to use the Festiva injector harness. You need to unwrap the harness and pull the green temp plug and the TPS plug back to the 1st injector plug and then rewrap the harness and install.

VAF Plug
The air box is located on the other side of the engine. You need to unwrap the harness quite a bit. I had to unplug the lights, horn to untangle the wires, this allowed me to bring the VAF harness to the other side.

VICS and PRC Solenoids
These are located on the passenger?s side of the manifold. The PRC (fuel pressure control solenoid) is already wired in the Festiva ECU. This plug is located under the wiper motor and is light brown in color. Just extend these 2 wires so that you can plug it into the PRC solenoid. Note: the common wire on the Festiva is yellow/black stripe wire and the BP common is white/red stripe wire.

The VICS (variable inertia charging system) solenoid is not in the Festiva harness. You need this plug from the donor vehicle. The white/red stripe wire is a common wire and can be spliced into the PRC common wire. The other wire goes to the ECU. If you look at the 26 pin ECU plug from the side the wire go in and with the release clip up it is the 4th wire from the left. This will be empty on the Festiva harness. I had the entire harness from my donor car so I unwrapped the BP harness and pulled this wire from the ECU plug. The ECU plug has a hinged flap that holds the wires in, just pry this up and yank (they are tight) the wire out and transfer this to the Festiva harness.

CID
This is the 4th wire on the BP distributor plug. The Festiva has 3 wires on the distributor plug. Cut the three wires from BP plug and remove the 4th from the ECU. It is the 10th wire from the left on the ECU (see VICS above). Cut the Festiva plug (1 at a time) and splice to the BP plug and then run the 4th wire to the ECU. This goes to the 10th hole on the Festiva ECU plug, there will be an empty spot there as well.

ISC
The idle speed control has a different plug. You will need to switch plugs, just cut them off and make sure that you leave enough to splice them back together. The ISC on the Festiva harness is light blue in color. When splicing the wire together make sure that the commons are spliced together. The Festiva common is the yellow/black stripe wire and the BP common is the white/red stripe wire, then splice the other 2.

Misc
The 2 temp sensors on the water neck are different. I just switched temperature sensors so that I could use the Festiva plugs. You also need to change the ECU. The Festiva is located behind the fuses box and is very difficult to get to. You will need to remove the heater hose that is below the ECU and then unplug the 2 ECU plugs. There are 2 bolts (10mm wrench) that need to be removed. Then slide the ECU up a bit and pull out and down, there is a little notch that the UCU bracket sits in. Once again it is very very tight in there.

Note: I have wired my car and it does run. This write up is from all that I found on the internet and from me tracing the VICS and CID wires on the BP harness to the ECU plug.