I'm having the same issue as civicEX442. I have a 99 Civic Si, and need to run a 4 gauge power wire.... but I have NO idea where in the firewall I can go through. Once I get it through the firewall, I'll be fine. If anyone knows of a good place to put a hole in the firewall, please let me know. I would ask about existing grommets... but I didn't think there would be one big enough for 4 gauge wire...