I just tried the passenger side large grommet to run power for a subwoofer and got through the little circle part with an exacto blade, but was hitting something beyond that point with my fiberglass rod. My son could see the wire bundle moving inside the vehicle but I could not push the fiberglass rod through. Any ideas what might be beyond the grommet? I’ve made several firewall pass throughs on other vehicles, this one should be easy. Thanks!