I have a broken bolt on my coil bracket that goes on the firewall. Can that be drilled out? Do I need to worry about how far in I drill for fear of hitting the gas tank?
You can drill it without any problem, but I'd first try the welding trick.
You weld a flat washer to the broken bolt, then weld a large nut to the flat washer. Let it cool for 5 minutes, then try working it back and forth. This has done the trick many times for me.
Usually when these bolts break, enough will protrude through the back side of the firewall that they can be backed out from the backside with pliers, vise grips if necessary. I've used this method before. good luck.