Unscrew that wiring harness off the firewall - makes it a ****load easier to pull the cable through. I pulled my 4 gauge cable through there and went behind the glovebox, then followed it down past the left side doors, under the rear seat, straight into the boot. Be sure to hold the cable in there tightly mate, bit of PVC tape wouldn't hurt. I managed to fit my cable through the same loom (tad tight... bit hard) but didn't have to cut anything though.