It's pretty easy to do on a Firebird. The circuit is designed so that the fog light relay trigger coil grounds through the highbeam circuit. When the highbeams are on there is 12V+ on both sides of the relay coil so that it doesn't engage (the fog lights go off). Find the fog light relay under the hood in junction box #1 along the inside of the left fender. The relay will have four wires - brown, yellow, purple and light green. Cut the light green wire and run the relay side to ground. Tape up the other side to prevent shorting. Now the relay has ground regardless of whether the highbeams are on so they will work normally but also stay on when using the highbeams.
I won't mention that this is illegal in most states (I don't know about Canada) because they don't allow more than four lights illuminated.
