Hyundai Elantra 2003 adding AMP, getting through firewall

I have a 2003 Elantra. I'm trying to get a 6 gauge wire ran through the firewall to connect an AMP in the trunk to the battery.
I'm having trouble finding a place to poke through. There is a place
near the brake wire where I could probably poke through, but that would exit me behind the brake booster, which is somewhat tight. I could remove the computer and poke through, but the computer is attached somewhat wierd. There is some sort of epoxy attaching it to the firewall and the firewall is cut and re-welded there, so I am a bit concerned about that. Anywhere else, and I'm looking at removing a lot more than I care to, afaik.
Anyone care to share how they went through the firewall? Thanks.
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Throttle cable grommet?
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I ran my power cable down the brake lines and under the car.
I ziptied them to the brake lines under the car the whole length, up and over the suspension, and into the grommet under the spare tire. Cover the cable with rubber if it touches any moving suspension parts, and leave enough slack, if applicable (I didn't need to). Works great. Shouldn't have any problems with it snagging if done correctly.
mandarin

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Wow. On the brake lines under the car or in the throttle grommet. Maybe I am paranoid, but I'm not certain I like those options. I worry the cable (it is 6 gauge) would make the throttle stick. I've seen bad things happen to wire ran under a car. Of course, that was wiring not done right. I don't know if I could do under the car correctly.
I think I'll try unscrewing the computer and drilling with a new bit at that location. There is nothing on the other side of the firewall there except for noise insulation. All my other cars that I've put amps in have had wiring grommets with enough space to add a power wire. Not this one, though.
Thanks for the ideas.
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