does anyone know the best place to run the power wire through the firewall in a 2011 Honda civic?

 

It's actually really close to the under dash fuse box, on the left-hand side of the car, not quite the firewall. There's a black grommet that leads out to the driver's side fender, and you can tuck it back up through the top of the fender through the engine bay. These pictures are from my USDM 2008 EX Coupe.

Driver's side fender 1 (fender liner pulled down):

Driver's side fender 2:


Under dash, it's slightly forward and to the left of the under dash fuse box. I highlighted the fuse box and clutch switch for reference. It's a PITA to get to:




Engine bay:



Hopefully this helps. I can't say the same for any euro or JDM spec, or sedans.