1999 ford expedition amp power cable?

Hi, Im helping a friend out and trying to install an amp and sub on his 1999 Ford Expedition with the Mach system. I need help in figuring out where to run the 4 guage power wire through the firewall.  Any ideas? If someone has pictures i will greatly appreciate it. Thanks in advance

anyone?

please????????????/

Sorry old boy, people here are generally more helpful. Maybe its because your post should have been placed in the "general discussion" section.....i dont know.... I  have gone through the firewall of many different vehicles many times but unfortunately I cant remember specifics on your vehicle. That being said, my approach is always the same. I usually can find a spot on the drivers side from inside the vehicle, so begin looking there. stick your head all the way in, a flashlight will be helpful. then look at the firewall, you may have to peel back the insulation to get a good look. next look for spare rubber gromet plugs with nothing going through, they will sometimes be there plugging a hole for some option your vehicle doesnt have or standard transmission parts etc... If nothing is visible, look for gromets with wires or cables going through ( I would try to stay away from the throttle cable for obvious reasons). You can sometimes fish your wire next to the cable quite easily. If not, many times there is enough room to slice your own hole with a razor knife or maybe pinch the rubber and cut it with a pair of cutters (be extremely careful not to cut any existing wires, it will be verrrrrrrrry difficult to make any repairs in such a confined space.) If you are unsuccessful, try the passenger side using the same techniques. If you are still unsuccessful......last resort........you can make your own hole. Again, be extremely careful and know exactly what is on the other side of your drill. you have to be precise. If not you will have a BIG MESS on your hands and the wire will be the least of you and your friends worries. BUT, dont be scared, just be certain. dont forget to use a rubber gromet and remember your fuse. Hope this helps. Good luck!

Thank you sir, i will start again this weekend on the drivers side. What i initially looked at was the passenger side, since i didnt want to hurt anything under the driver side. I will post up my conclusion..thanks again for your kind help. 

Thank you guys so much!