I ran my power cable not through the firewall but through the inner fender. the firewall is tucked in under the dashboard so I found an alternative.
right behind the side markers there's a gromet where the harness went inside the car. This is also where the hood release cable and foglight harness went through. I removed the fender liner and pricked a hole through the gromet using a screwdriver.
Then ran the cable as you would normally do...
Here's a pic of my install...
http://www.clubae.proboards104.com/i...ead=1166428579