Hi all, I've converted my rear fogs to brake lamps for quite some years without any hassle. First of all you need to order a new bulb holder and cover as you need it to be dual filament. If you can remember, when you want to change a bulb you twist it and it pops out of the cover, right? Well, sods law the shape of the receiver (fog lamp cover) is a different shape so its not just a case of buying just the dual filament holder on its own. I managed to find some schematics and order it from Toyota Hong Kong. I was asking as a Altezza customer as its standard on that car. Once I got the complete set, luckily I had a friend who works for lexus (engineer) and for a small charge he managed to rewire my fog lamps to match my brake lamps. He also rewired the existing fog lamps cable down the back of the car behind the bumper so that I can attach an external fog lamp (like the import cars) when needed e.g for MOT testing. As you have gathered, I have taken my external fogs off the car during the year and only put it back on for MOT or if its really foggy so not to ruin the car's look. The fitting takes 5 mins and is really easy. The external fog lamp fits nicely under the car using a bolt and a hole under the bumper. You can see this 'flap with a hole' if you look underneath.
I must say that this conversion makes the car look so much more aggressive and is a head turner!
I've never had problems with lights on the dash saying there is a problem with the bulbs. When i dont use the external fogs, I simply tape up the wire in masking tape and tuck it behind the bumper!
Oh btw, you also have to purchase a pair of dual filament bulbs (same as the brake bulbs). Sorry to waffle but hope that helps. I will try and get some pics posted up.