Someone on here was recently asking about why only one of the rear fog lights works on the 406. The answer is that you are only required to have 1 rear fog by law, so why have 2 "spaces" in the clusters? It's just untidy!
This inspired me to do a bit of fiddling on the weekend. Got the panel off the inside of the tailgate and noted that the wiring to both clusters looked exactly the same, so I popped the near side cluster out and took a look. Sure enough there's a vacant bulb holder there. Fitted a bulb, plugged it back in (just hanging from the wires under the tailgate and switched the fogs on, and yay, two fogs!!
Nice enough, I'll put it back together then. Oh no, it ain't that easy, they've only gone and made the hole in the back of the cluster undersized on purpose, so that if you fit a bulb in the fog light holder, you cant get the back plate back onto the cluster. Not about to be beaten by such an obvious pre-planned attempt by the viscious bastards at peugeot to spoil my afternoon, I got the dremmel out and butchered the fekkin thing!!!!
So yay, two fogs!
). Think I may take the dremmel to mine too now 
Wonderful things, you can use 'em to chew straight through solid aluminium just on the weight of the dremmel