"Somewhat related? As a somewhat related side note, many people ask where they should route the vacuum line through the firewall to run the boost gauge. I ran mine through the speedometer cable hole. This hole is located slightly below the brake master cylinder. The hole is much bigger than the actual speedometer cable, so there is plenty of room. The cable is surrounded by a rubber grommet that you can pull out towards the engine to open up the hole. Once you get a few wires in there, the rubber grommet will no longer fit, so you will have to close up the hole some other way if you want to. The advantage of using this hole is that you do not have to cut up the car at all, and the hoses, wires, or whatever come through the firewall up high behind the brake pedal. They will be accessable if you lay in your drivers side floor and reach up. They will be out of site and out of the pedal travel path. Here is a picture of the hole from the engine side. (TS- note, if you run wires through here, it is best to slit the grommet and run the wires through the slit. If you have many wires and can't use the grommet, make sure to run several layers of tape over the wires for several inches before and after the hole to make sure that the wires don't rub the hole and get cut.)"
