Im going to install a system for my friends 05 mustang. I was wondering if there was a way to run the 4 awg wiring from the battery to the trunk without having to drill through the firewall. If so, can somebody let me know where i can run the wire through. If you have pics, that would be nice, or even a diy link. thanks.

 

Look closely at the firewall. Usually, there is a few extra holes already in the firewall. They are plugged with a rubber plug. Find one of these rubber plugs remove it and cut a hole in the rubber plug. Run the wire through the rubber plug and the hole in the fire wall, and then replace the plug in the hole.