i've got a 2006 sierra, with fogs... what I did was solder up 2 diodes with small gauge wires on both ends, shrink wrapped them.
Then, I took the banded side of the first one and ran it from the 85 pin of my low beam light plug in the fuse box (under hood) and connected the other end to my 85 pin fog light plug.
this makes my fogs come on automatically with my low beams.
Then, I took the other diode, wrapped the banded side of the diode to the 85 pin connector for the highbeam plug in the fuse block, and ran the other to the 85 pin of the low beams plug (so there's 2 wires wrapped on there).
This will keep my low beams on while high beams are on.... and, since I had the first diode connected, it also lights my fog lights... there's 6 lights for highway driving (same as pulling the highbeam stalk towards you to the "flash-to-pass")
I LOVE THIS MOD.. and it only costs about 5 bucks. good on 2002 chevs and up