I need to run a cable through the firewall. I found the huge rubber grommet on the passanger side but it's a pain to get to and I don't think I can run another cable in there. I read somewhere about a foam seal that you can run a cable through on the passager side where the dash meets the frame. I took of that cover and put a screwdriver through the hole but I can't figure out where it goes. What do I do?