There is a large grommet through the firewall on each side of the car. To access it you need to take off the front wheel and remove the rear half of the fender inner liner. To remove the liner, there are about 6 reuseable push-type body pins. Use a small flat screw driver to pry out the center lock of each pin then pull pin out. To reach an amp in the trunk you could go through the passenger side firewall, under the door sill plate, under the rear seat, and into the trunk.