I ran my 4 gauge wire through the factory rubber grommet that originaly had the speedo cable running through it. Then like everyone else, I ran the wire through the plastic channel along the sill under the carpet and back into the trunk.
Biggest thing to remember is that you want your power wires on the opposite side of the car from the speaker/signal wires so that you don't introduce any interference as mentioned above.
Biggest thing to remember is that you want your power wires on the opposite side of the car from the speaker/signal wires so that you don't introduce any interference as mentioned above.