Some people run them inside the car and some run them outside. What i would do (and plan on doing) is running it out of the trunk (i believe there are already places to run it out w/o having to drill a hole) and following the fuel lines down the frame
Yeah, I know...The problem I am having right now is that I mounted my bottle on my driver side in my trunk and my solenoids by where my strut tower brace bolts in...I have a 15 foot line (odd number I know but I measured it) but I tried to somewhat run the line and it doesnt seem like it is going to be long enough (Out the trunk and under the car). So I was thinking of running it the same way I ran my electrical, which was up through the back seat and up through the grommet in the firewall on the driver side and then run the line along the back under the hood and to the solenoids. I think that way it will actually reach. But I just wanted a few ideas.