Firewall openings I am trying to run a power cable for an amplifier from the battery through the firewall and eventually to the trunk of the car... However after a lot of searching I have yet to find any opening that an 8 Gauge wire can pass through... If anyone knows of an opening that i can try to look for or of any easy way of solving this predicament I would be greatly appreciative. Thanks

Check your owners manual, there is usually a manual cable inside of the vehicle to release the trunk for just such an instance.

Read the alarm installation manual carefully and keep the support number handy if you have any questions as every alarm manufacturer uses different connection and mounting techniques. Open the hood and disconnect the positive battery cable. Connect the alarm power wire to the positive battery cable and run it to the driver side of the firewall.
Locate an open area in the engine bay and mount the siren, facing the engine to limit water exposure while driving. Run the siren wires to the driver side's of the firewall and feed all of the wires through the firewall and into the dash area of the Impala. Drill a small hole in the firewall if necessary, directly in front of the steering wheel.
Remove the lower dash panel if necessary and mount the shock sensor per the manufacturer's instructions. Locate the power lock relay if the car is so equipped and connect the alarm's power lock module.
Find the starter wire in the ignition harness and attach the start disable relay. Drill a small hole in the dash for the LED light and snap it into place.
Connect all of the wires to the alarm control module by plugging them into the module and secure it as far into the dash as possible with zip ties.
Reconnect the positive battery and test the alarm on the Impala. Adjust the sensitivity level as desired and secure any loose wires with zip ties.
Original Mercedes Benz NEC PRO57 Support Online Update

Use jumper cables from another car-put the positive jumper cable on the post on the starter where the battery cable connects, then the negative jumper cable to a ground on the frame of your car. Turn on the car you are jumping with and let it run about 10 minutes. It might charge up your battery in the trunk enough to open the trunk.

The best or more professional way to run the cables is to drill a hole thru the firewall. You need to use wire ties on the cables and route the cables along the factory wiring harness. Try to route to the shortest distance and use a rubber grommet where you have the hole drilled in the firewall. The grommet will keep the cable from getting damaged by the sharp edges of the hole that you drilled. Also the largest possible diameter cable is better because you will get more amperage to the power inverter. Hope this helps :)

Try looking to where your bundled wire harness, almost looks like a huge power cable goes from the engine compartment into the firewall.

if the battery is on the drivers side then there should already be a grommet there near the steering column.
if you locate one all you need to do is make a **** with a razor to slide the cable through.

you should run it through the same side as the battery and if there is no grommet there you will need to drill a hole and install a grommet your self.

keep the fuse less than 18" from the battery connection.

if you have any more questions please ask and sorry to be vague but never did a install on this car but this is the by thumb rules you need to follow. good luck.

Can't say I've done what your doing but have had to run cables directly to battery for power inside, and I've used boot by steering column, on firewall, as well as any other grommet in the area that has some room, and carefully made a small **** with utility knife, and fed cable through it. On occasion that no grommet or other was available, I carefully surveyed area of firewall where no wires etc, would be in line, and bought some undercoating plugs from autoparts store, drilled a hole in firewall, proper size, inserted the plug, and made small ****, and ran my cables through it. Probably don't need to say it but i will, if going direct to battery, be sure to fuse it in line properly.

cover under bonnet with a big P on it and negative is anything metal on the engine

jump start the car or charge the battery from under the bonnet(hood) ,look for a plastic cover on the firewall with a big + on it negative is the engine

look inside of the dash there should be a release by the firewall