Theres some good information about this tucked into different threads, I wanted to make a easy post for anyone wishing to get some wires cleanly through the firewall for an amp/gauges/lighting/etc. without any new holes. (Also nice to have images that are still linked!)

The two best options I found are utilizing where the oem harness goes through the firewall on the passenger or drivers side. Neither options have great access from both sides. The drivers side is accesible mainly from under the dashboard. remove the panel for fusebox access and the under dash cover panel. The harness is also viewable from the engine bay with limited access, as it is behind the drivers strut tower. The passenger side harness is accessible with reasonable space from the engine bay next to the passenger strut tower. I chose this side. Tools I used: bent pliers, razor blade, electrical tape. I ran 3 wires for gauge sending units, and 2 incase I want any accessories later.

You can route the wires through bulkhead grommet by removing the many layers of tape sealing the harness to the grommet from the engine bay side. Bunch your wires together and shove them through the grommet (some soapy water helps). The wires will come out under the glovebox onto the floor. Removing the panel under the glovebox (held by clips) lets you tuck the wires very cleanly. Add some wiring wrap inside the engine bay and retape the harness to the grommet and it should look like you were never there!




wires fed through the grommet

new wires covered in a loom and taped

new wires zip tied to blower wires to keep it neat & tidy