For those who have had to, please let me know where you have sent wires through the firewall on your foci. I am installing an alarm and just wanted to get an idea as to what the best place is to do that.
I've gone thru a rubber plug underneath the door wiring harness on the driver's side(when you open the door, underneath the plastic tube looking thing) then routed towards the inside of the fender, after that a hole was drilled big enough for the wires to go thru. Then you can just put a rubber seal on there to keep from any possible leaks to happen.
If you look up at the top of the strut tower from inside the fender (with the splash shield removed) there's a hole that opens into the fender. When I installed my cruise control kit, I ran the wires through the rubber plug on the driver's side, through the fender and through the hole into the engine compartment. If you have a rubber boot going to the door on both holes you could just cut a slit in the boot and pass the cables out the same way. Otherwise, drilling through the firewall is a pain in the ass because the only places you can drill through are at the bottom of the car, and the metal is pretty thick through there.
yo easest place to go trough is by the steering colom, look from the inside right above where the streeing wheel goes trough you will see a 2 by 4 rectangle cut out in the foam remove it there is a plastic gromit type thing there u can just drill a hole trough that can send pic if u need comes out right behind the exhaust manifold.
I ran the 2 x #8 feeds for my amps through the bulkhead connector inside the driver's fenderwell by drilling holes in the dead spots. There is sufficient room for more wires if needed, but the hole has to be completely sealed because water will get in that area.
Remove the wheel, remove the plastic inner fenderwell, and then remove the foam pad. If you look up inside the fenderwell back towards the car you will see the bulkhead connector with a 10mm bolt holding it together. Look under the dash, and you'll see the other side of the connector. Unbolt the connector, and it will unplug from inside the fenderwell. Now push the clips that hold the other side of the connector in the firewall and it will fall out under the dash. There should be an intermediary part that goes between the two connectors like a sleeve- if my memory is right, this is in two parts and is held in place by the bulkhead connectors. Examine the parts to find the correct orientation, and drill a hole where it will not interfere with the factory wiring. Replace the bulkhead connector, bolt the halves in place, and run your wire. Factory wiring runs under the carpet, inside the car, and beside the doors. There is ample room under the formed carpet to run all sorts of wiring, but the door sills and carpet are a pain to pull up. The sills pull straight up using your hands and a lot of force- expect to possibly break a peg. Also be careful that the metal clips are on the pegs and not stuck in the door before installing. The carpet clips pull straight up also, with even more force- be sure to put your hands as close as possible to the plastic clips on the carpet. None of these tore on my car, but I did hit my head on the roof when one pulled up suddenly.
Also a 99¢ packet of spark plug boot grease is recommended for when you re-install the bulkhead connector. Spread some on all the pins before installing for added water/ corrosion protection.